x86: Fix up x86_{,64_}sh{l,r}d patterns [PR103431]

The following testcase is miscompiled because the x86_{,64_}sh{l,r}d
patterns don't properly describe what the instructions do.  One thing
is left out, in particular that there is initial count &= 63 for
sh{l,r}dq and initial count &= 31 for sh{l,r}d{l,w}.  And another thing
not described properly, in particular the behavior when count (after the
masking) is 0.  The pattern says it is e.g.
res = (op0 << op2) | (op1 >> (64 - op2))
but that triggers UB on op1 >> 64.  For op2 0 we actually want
res = (op0 << op2) | 0
When constants are propagated to these patterns during RTL optimizations,
both such problems trigger wrong-code issues.
This patch represents the patterns as e.g.
res = (op0 << (op2 & 63)) | (unsigned long long) ((uint128_t) op1 >> (64 - (op2 & 63)))
so there is both the initial masking and op2 == 0 behavior results in
zero being ored.
The patch introduces alternate patterns for constant op2 where
simplify-rtx.c will fold those expressions into simple numbers,
and define_insn_and_split pre-reload splitter for how the patterns
looked before into the new form, so that it can pattern match during
combine even computations that assumed the shift amount will be in
the range of 1 .. bitsize-1.

2021-11-27  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/103431
	* config/i386/i386.md (x86_64_shld, x86_shld, x86_64_shrd, x86_shrd):
	Change insn pattern to accurately describe the instructions.
	(*x86_64_shld_1, *x86_shld_1, *x86_64_shrd_1, *x86_shrd_1): New
	define_insn patterns.
	(*x86_64_shld_2, *x86_shld_2, *x86_64_shrd_2, *x86_shrd_2): New
	define_insn_and_split patterns.
	(*ashl<dwi>3_doubleword_mask, *ashl<dwi>3_doubleword_mask_1,
	*<insn><dwi>3_doubleword_mask, *<insn><dwi>3_doubleword_mask_1,
	ix86_rotl<dwi>3_doubleword, ix86_rotr<dwi>3_doubleword): Adjust
	splitters for x86_{,64_}sh{l,r}d pattern changes.

	* gcc.dg/pr103431.c: New test.

2 files changed, 281 insertions, 42 deletions

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 68606e5..24368c7 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -11301,9 +11301,12 @@
   "&& 1"
   [(parallel
      [(set (match_dup 6)
-	   (ior:DWIH (ashift:DWIH (match_dup 6) (match_dup 2))
-		     (lshiftrt:DWIH (match_dup 5)
-		       (minus:QI (match_dup 8) (match_dup 2)))))
+	   (ior:DWIH (ashift:DWIH (match_dup 6)
+		       (and:QI (match_dup 2) (match_dup 8)))
+		     (subreg:DWIH
+		       (lshiftrt:<DWI> (zero_extend:<DWI> (match_dup 5))
+			 (minus:QI (match_dup 9)
+				   (and:QI (match_dup 2) (match_dup 8)))) 0)))
       (clobber (reg:CC FLAGS_REG))])
    (parallel
      [(set (match_dup 4)
@@ -11312,7 +11315,8 @@
 {
   split_double_mode (<DWI>mode, &operands[0], 2, &operands[4], &operands[6]);
 
-  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
+  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT - 1);
+  operands[9] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
 
   if ((INTVAL (operands[3]) & ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
       != ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
@@ -11342,9 +11346,12 @@
   "&& 1"
   [(parallel
      [(set (match_dup 6)
-	   (ior:DWIH (ashift:DWIH (match_dup 6) (match_dup 2))
-		     (lshiftrt:DWIH (match_dup 5)
-		       (minus:QI (match_dup 8) (match_dup 2)))))
+	   (ior:DWIH (ashift:DWIH (match_dup 6)
+		       (and:QI (match_dup 2) (match_dup 8)))
+		     (subreg:DWIH
+		       (lshiftrt:<DWI> (zero_extend:<DWI> (match_dup 5))
+			 (minus:QI (match_dup 9)
+				   (and:QI (match_dup 2) (match_dup 8)))) 0)))
       (clobber (reg:CC FLAGS_REG))])
    (parallel
      [(set (match_dup 4)
@@ -11353,7 +11360,8 @@
 {
   split_double_mode (<DWI>mode, &operands[0], 2, &operands[4], &operands[6]);
 
-  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
+  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT - 1);
+  operands[9] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
 
   if ((INTVAL (operands[3]) & ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
       != ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
@@ -11404,9 +11412,14 @@
 (define_insn "x86_64_shld"
   [(set (match_operand:DI 0 "nonimmediate_operand" "+r*m")
         (ior:DI (ashift:DI (match_dup 0)
-		  (match_operand:QI 2 "nonmemory_operand" "Jc"))
-		(lshiftrt:DI (match_operand:DI 1 "register_operand" "r")
-		  (minus:QI (const_int 64) (match_dup 2)))))
+		  (and:QI (match_operand:QI 2 "nonmemory_operand" "Jc")
+			  (const_int 63)))
+		(subreg:DI
+		  (lshiftrt:TI
+		    (zero_extend:TI
+		      (match_operand:DI 1 "register_operand" "r"))
+		    (minus:QI (const_int 64)
+			      (and:QI (match_dup 2) (const_int 63)))) 0)))
    (clobber (reg:CC FLAGS_REG))]
   "TARGET_64BIT"
   "shld{q}\t{%s2%1, %0|%0, %1, %2}"
@@ -11417,12 +11430,58 @@
    (set_attr "amdfam10_decode" "vector")
    (set_attr "bdver1_decode" "vector")])
 
+(define_insn "*x86_64_shld_1"
+  [(set (match_operand:DI 0 "nonimmediate_operand" "+r*m")
+        (ior:DI (ashift:DI (match_dup 0)
+			   (match_operand:QI 2 "const_0_to_63_operand" "J"))
+		(subreg:DI
+		  (lshiftrt:TI
+		    (zero_extend:TI
+		      (match_operand:DI 1 "register_operand" "r"))
+		    (match_operand:QI 3 "const_0_to_255_operand" "N")) 0)))
+   (clobber (reg:CC FLAGS_REG))]
+  "TARGET_64BIT
+   && INTVAL (operands[3]) == 64 - INTVAL (operands[2])"
+  "shld{q}\t{%2, %1, %0|%0, %1, %2}"
+  [(set_attr "type" "ishift")
+   (set_attr "prefix_0f" "1")
+   (set_attr "mode" "DI")
+   (set_attr "athlon_decode" "vector")
+   (set_attr "amdfam10_decode" "vector")
+   (set_attr "bdver1_decode" "vector")])
+
+(define_insn_and_split "*x86_64_shld_2"
+  [(set (match_operand:DI 0 "nonimmediate_operand")
+	(ior:DI (ashift:DI (match_dup 0)
+			   (match_operand:QI 2 "nonmemory_operand"))
+		(lshiftrt:DI (match_operand:DI 1 "register_operand")
+			     (minus:QI (const_int 64) (match_dup 2)))))
+   (clobber (reg:CC FLAGS_REG))]
+  "TARGET_64BIT && ix86_pre_reload_split ()"
+  "#"
+  "&& 1"
+  [(parallel [(set (match_dup 0)
+		   (ior:DI (ashift:DI (match_dup 0)
+				      (and:QI (match_dup 2) (const_int 63)))
+			   (subreg:DI
+			     (lshiftrt:TI
+			       (zero_extend:TI (match_dup 1))
+				 (minus:QI (const_int 64)
+					   (and:QI (match_dup 2)
+						   (const_int 63)))) 0)))
+	      (clobber (reg:CC FLAGS_REG))])])
+
 (define_insn "x86_shld"
   [(set (match_operand:SI 0 "nonimmediate_operand" "+r*m")
         (ior:SI (ashift:SI (match_dup 0)
-		  (match_operand:QI 2 "nonmemory_operand" "Ic"))
-		(lshiftrt:SI (match_operand:SI 1 "register_operand" "r")
-		  (minus:QI (const_int 32) (match_dup 2)))))
+		  (and:QI (match_operand:QI 2 "nonmemory_operand" "Ic")
+			  (const_int 31)))
+		(subreg:SI
+		  (lshiftrt:DI
+		    (zero_extend:DI
+		      (match_operand:SI 1 "register_operand" "r"))
+		    (minus:QI (const_int 32)
+			      (and:QI (match_dup 2) (const_int 31)))) 0)))
    (clobber (reg:CC FLAGS_REG))]
   ""
   "shld{l}\t{%s2%1, %0|%0, %1, %2}"
@@ -11434,6 +11493,47 @@
    (set_attr "amdfam10_decode" "vector")
    (set_attr "bdver1_decode" "vector")])
 
+(define_insn "*x86_shld_1"
+  [(set (match_operand:SI 0 "nonimmediate_operand" "+r*m")
+        (ior:SI (ashift:SI (match_dup 0)
+			   (match_operand:QI 2 "const_0_to_31_operand" "I"))
+		(subreg:SI
+		  (lshiftrt:DI
+		    (zero_extend:DI
+		      (match_operand:SI 1 "register_operand" "r"))
+		    (match_operand:QI 3 "const_0_to_63_operand" "J")) 0)))
+   (clobber (reg:CC FLAGS_REG))]
+  "INTVAL (operands[3]) == 32 - INTVAL (operands[2])"
+  "shld{l}\t{%2, %1, %0|%0, %1, %2}"
+  [(set_attr "type" "ishift")
+   (set_attr "prefix_0f" "1")
+   (set_attr "mode" "SI")
+   (set_attr "pent_pair" "np")
+   (set_attr "athlon_decode" "vector")
+   (set_attr "amdfam10_decode" "vector")
+   (set_attr "bdver1_decode" "vector")])
+
+(define_insn_and_split "*x86_shld_2"
+  [(set (match_operand:SI 0 "nonimmediate_operand")
+	(ior:SI (ashift:SI (match_dup 0)
+			   (match_operand:QI 2 "nonmemory_operand"))
+		(lshiftrt:SI (match_operand:SI 1 "register_operand")
+			     (minus:QI (const_int 32) (match_dup 2)))))
+   (clobber (reg:CC FLAGS_REG))]
+  "TARGET_64BIT && ix86_pre_reload_split ()"
+  "#"
+  "&& 1"
+  [(parallel [(set (match_dup 0)
+		   (ior:SI (ashift:SI (match_dup 0)
+				      (and:QI (match_dup 2) (const_int 31)))
+			   (subreg:SI
+			     (lshiftrt:DI
+			       (zero_extend:DI (match_dup 1))
+				 (minus:QI (const_int 32)
+					   (and:QI (match_dup 2)
+						   (const_int 31)))) 0)))
+	      (clobber (reg:CC FLAGS_REG))])])
+
 (define_expand "@x86_shift<mode>_adj_1"
   [(set (reg:CCZ FLAGS_REG)
 	(compare:CCZ (and:QI (match_operand:QI 2 "register_operand")
@@ -12080,9 +12180,12 @@
   "&& 1"
   [(parallel
      [(set (match_dup 4)
-	   (ior:DWIH (lshiftrt:DWIH (match_dup 4) (match_dup 2))
-		     (ashift:DWIH (match_dup 7)
-		       (minus:QI (match_dup 8) (match_dup 2)))))
+	   (ior:DWIH (lshiftrt:DWIH (match_dup 4)
+		       (and:QI (match_dup 2) (match_dup 8)))
+		     (subreg:DWIH
+		       (ashift:<DWI> (zero_extend:<DWI> (match_dup 7))
+			 (minus:QI (match_dup 9)
+				   (and:QI (match_dup 2) (match_dup 8)))) 0)))
       (clobber (reg:CC FLAGS_REG))])
    (parallel
      [(set (match_dup 6)
@@ -12091,7 +12194,8 @@
 {
   split_double_mode (<DWI>mode, &operands[0], 2, &operands[4], &operands[6]);
 
-  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
+  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT - 1);
+  operands[9] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
 
   if ((INTVAL (operands[3]) & ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
       != ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
@@ -12121,9 +12225,12 @@
   "&& 1"
   [(parallel
      [(set (match_dup 4)
-	   (ior:DWIH (lshiftrt:DWIH (match_dup 4) (match_dup 2))
-		     (ashift:DWIH (match_dup 7)
-		       (minus:QI (match_dup 8) (match_dup 2)))))
+	   (ior:DWIH (lshiftrt:DWIH (match_dup 4)
+		       (and:QI (match_dup 2) (match_dup 8)))
+		     (subreg:DWIH
+		       (ashift:<DWI> (zero_extend:<DWI> (match_dup 7))
+			 (minus:QI (match_dup 9)
+				   (and:QI (match_dup 2) (match_dup 8)))) 0)))
       (clobber (reg:CC FLAGS_REG))])
    (parallel
      [(set (match_dup 6)
@@ -12132,7 +12239,8 @@
 {
   split_double_mode (<DWI>mode, &operands[0], 2, &operands[4], &operands[6]);
 
-  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
+  operands[8] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT - 1);
+  operands[9] = GEN_INT (<MODE_SIZE> * BITS_PER_UNIT);
 
   if ((INTVAL (operands[3]) & ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
       != ((<MODE_SIZE> * BITS_PER_UNIT) - 1))
@@ -12177,9 +12285,14 @@
 (define_insn "x86_64_shrd"
   [(set (match_operand:DI 0 "nonimmediate_operand" "+r*m")
         (ior:DI (lshiftrt:DI (match_dup 0)
-		  (match_operand:QI 2 "nonmemory_operand" "Jc"))
-		(ashift:DI (match_operand:DI 1 "register_operand" "r")
-		  (minus:QI (const_int 64) (match_dup 2)))))
+		  (and:QI (match_operand:QI 2 "nonmemory_operand" "Jc")
+			  (const_int 63)))
+		(subreg:DI
+		  (ashift:TI
+		    (zero_extend:TI
+		      (match_operand:DI 1 "register_operand" "r"))
+		    (minus:QI (const_int 64)
+			      (and:QI (match_dup 2) (const_int 63)))) 0)))
    (clobber (reg:CC FLAGS_REG))]
   "TARGET_64BIT"
   "shrd{q}\t{%s2%1, %0|%0, %1, %2}"
@@ -12190,12 +12303,58 @@
    (set_attr "amdfam10_decode" "vector")
    (set_attr "bdver1_decode" "vector")])
 
+(define_insn "*x86_64_shrd_1"
+  [(set (match_operand:DI 0 "nonimmediate_operand" "+r*m")
+        (ior:DI (lshiftrt:DI (match_dup 0)
+			     (match_operand:QI 2 "const_0_to_63_operand" "J"))
+		(subreg:DI
+		  (ashift:TI
+		    (zero_extend:TI
+		      (match_operand:DI 1 "register_operand" "r"))
+		    (match_operand:QI 3 "const_0_to_255_operand" "N")) 0)))
+   (clobber (reg:CC FLAGS_REG))]
+  "TARGET_64BIT
+   && INTVAL (operands[3]) == 64 - INTVAL (operands[2])"
+  "shrd{q}\t{%2, %1, %0|%0, %1, %2}"
+  [(set_attr "type" "ishift")
+   (set_attr "prefix_0f" "1")
+   (set_attr "mode" "DI")
+   (set_attr "athlon_decode" "vector")
+   (set_attr "amdfam10_decode" "vector")
+   (set_attr "bdver1_decode" "vector")])
+
+(define_insn_and_split "*x86_64_shrd_2"
+  [(set (match_operand:DI 0 "nonimmediate_operand")
+	(ior:DI (lshiftrt:DI (match_dup 0)
+			     (match_operand:QI 2 "nonmemory_operand"))
+		(ashift:DI (match_operand:DI 1 "register_operand")
+			   (minus:QI (const_int 64) (match_dup 2)))))
+   (clobber (reg:CC FLAGS_REG))]
+  "TARGET_64BIT && ix86_pre_reload_split ()"
+  "#"
+  "&& 1"
+  [(parallel [(set (match_dup 0)
+		   (ior:DI (lshiftrt:DI (match_dup 0)
+					(and:QI (match_dup 2) (const_int 63)))
+			   (subreg:DI
+			     (ashift:TI
+			       (zero_extend:TI (match_dup 1))
+				 (minus:QI (const_int 64)
+					   (and:QI (match_dup 2)
+						   (const_int 63)))) 0)))
+	      (clobber (reg:CC FLAGS_REG))])])
+
 (define_insn "x86_shrd"
   [(set (match_operand:SI 0 "nonimmediate_operand" "+r*m")
         (ior:SI (lshiftrt:SI (match_dup 0)
-		  (match_operand:QI 2 "nonmemory_operand" "Ic"))
-		(ashift:SI (match_operand:SI 1 "register_operand" "r")
-		  (minus:QI (const_int 32) (match_dup 2)))))
+		  (and:QI (match_operand:QI 2 "nonmemory_operand" "Ic")
+			  (const_int 31)))
+		(subreg:SI
+		  (ashift:DI
+		    (zero_extend:DI
+		      (match_operand:SI 1 "register_operand" "r"))
+		    (minus:QI (const_int 32)
+			      (and:QI (match_dup 2) (const_int 31)))) 0)))
    (clobber (reg:CC FLAGS_REG))]
   ""
   "shrd{l}\t{%s2%1, %0|%0, %1, %2}"
@@ -12207,6 +12366,47 @@
    (set_attr "amdfam10_decode" "vector")
    (set_attr "bdver1_decode" "vector")])
 
+(define_insn "*x86_shrd_1"
+  [(set (match_operand:SI 0 "nonimmediate_operand" "+r*m")
+        (ior:SI (lshiftrt:SI (match_dup 0)
+			     (match_operand:QI 2 "const_0_to_31_operand" "I"))
+		(subreg:SI
+		  (ashift:DI
+		    (zero_extend:DI
+		      (match_operand:SI 1 "register_operand" "r"))
+		    (match_operand:QI 3 "const_0_to_63_operand" "J")) 0)))
+   (clobber (reg:CC FLAGS_REG))]
+  "INTVAL (operands[3]) == 32 - INTVAL (operands[2])"
+  "shrd{l}\t{%2, %1, %0|%0, %1, %2}"
+  [(set_attr "type" "ishift")
+   (set_attr "prefix_0f" "1")
+   (set_attr "mode" "SI")
+   (set_attr "pent_pair" "np")
+   (set_attr "athlon_decode" "vector")
+   (set_attr "amdfam10_decode" "vector")
+   (set_attr "bdver1_decode" "vector")])
+
+(define_insn_and_split "*x86_shrd_2"
+  [(set (match_operand:SI 0 "nonimmediate_operand")
+	(ior:SI (lshiftrt:SI (match_dup 0)
+			     (match_operand:QI 2 "nonmemory_operand"))
+		(ashift:SI (match_operand:SI 1 "register_operand")
+			   (minus:QI (const_int 32) (match_dup 2)))))
+   (clobber (reg:CC FLAGS_REG))]
+  "TARGET_64BIT && ix86_pre_reload_split ()"
+  "#"
+  "&& 1"
+  [(parallel [(set (match_dup 0)
+		   (ior:SI (lshiftrt:SI (match_dup 0)
+					(and:QI (match_dup 2) (const_int 31)))
+			   (subreg:SI
+			     (ashift:DI
+			       (zero_extend:DI (match_dup 1))
+				 (minus:QI (const_int 32)
+					   (and:QI (match_dup 2)
+						   (const_int 31)))) 0)))
+	      (clobber (reg:CC FLAGS_REG))])])
+
 ;; Base name for insn mnemonic.
 (define_mode_attr cvt_mnemonic
   [(SI "{cltd|cdq}") (DI "{cqto|cqo}")])
@@ -12784,18 +12984,27 @@
  [(set (match_dup 3) (match_dup 4))
   (parallel
    [(set (match_dup 4)
-	 (ior:DWIH (ashift:DWIH (match_dup 4) (match_dup 2))
-		   (lshiftrt:DWIH (match_dup 5)
-				  (minus:QI (match_dup 6) (match_dup 2)))))
+	 (ior:DWIH (ashift:DWIH (match_dup 4)
+				(and:QI (match_dup 2) (match_dup 6)))
+		   (subreg:DWIH
+		     (lshiftrt:<DWI> (zero_extend:<DWI> (match_dup 5))
+				     (minus:QI (match_dup 7)
+					       (and:QI (match_dup 2)
+						       (match_dup 6)))) 0)))
     (clobber (reg:CC FLAGS_REG))])
   (parallel
    [(set (match_dup 5)
-	 (ior:DWIH (ashift:DWIH (match_dup 5) (match_dup 2))
-		   (lshiftrt:DWIH (match_dup 3)
-				  (minus:QI (match_dup 6) (match_dup 2)))))
+	 (ior:DWIH (ashift:DWIH (match_dup 5)
+				(and:QI (match_dup 2) (match_dup 6)))
+		   (subreg:DWIH
+		     (lshiftrt:<DWI> (zero_extend:<DWI> (match_dup 3))
+				     (minus:QI (match_dup 7)
+					       (and:QI (match_dup 2)
+						       (match_dup 6)))) 0)))
     (clobber (reg:CC FLAGS_REG))])]
 {
-  operands[6] = GEN_INT (GET_MODE_BITSIZE (<MODE>mode));
+  operands[6] = GEN_INT (GET_MODE_BITSIZE (<MODE>mode) - 1);
+  operands[7] = GEN_INT (GET_MODE_BITSIZE (<MODE>mode));
 
   split_double_mode (<DWI>mode, &operands[0], 1, &operands[4], &operands[5]);
 })
@@ -12812,18 +13021,27 @@
  [(set (match_dup 3) (match_dup 4))
   (parallel
    [(set (match_dup 4)
-	 (ior:DWIH (lshiftrt:DWIH (match_dup 4) (match_dup 2))
-		   (ashift:DWIH (match_dup 5)
-				(minus:QI (match_dup 6) (match_dup 2)))))
+	 (ior:DWIH (lshiftrt:DWIH (match_dup 4)
+				  (and:QI (match_dup 2) (match_dup 6)))
+		   (subreg:DWIH
+		     (ashift:<DWI> (zero_extend:<DWI> (match_dup 5))
+				   (minus:QI (match_dup 7)
+					     (and:QI (match_dup 2)
+						     (match_dup 6)))) 0)))
     (clobber (reg:CC FLAGS_REG))])
   (parallel
    [(set (match_dup 5)
-	 (ior:DWIH (lshiftrt:DWIH (match_dup 5) (match_dup 2))
-		   (ashift:DWIH (match_dup 3)
-				(minus:QI (match_dup 6) (match_dup 2)))))
+	 (ior:DWIH (lshiftrt:DWIH (match_dup 5)
+				  (and:QI (match_dup 2) (match_dup 6)))
+		   (subreg:DWIH
+		     (ashift:<DWI> (zero_extend:<DWI> (match_dup 3))
+				   (minus:QI (match_dup 7)
+					     (and:QI (match_dup 2)
+						     (match_dup 6)))) 0)))
     (clobber (reg:CC FLAGS_REG))])]
 {
-  operands[6] = GEN_INT (GET_MODE_BITSIZE (<MODE>mode));
+  operands[6] = GEN_INT (GET_MODE_BITSIZE (<MODE>mode) - 1);
+  operands[7] = GEN_INT (GET_MODE_BITSIZE (<MODE>mode));
 
   split_double_mode (<DWI>mode, &operands[0], 1, &operands[4], &operands[5]);
 })
diff --git a/gcc/testsuite/gcc.dg/pr103431.c b/gcc/testsuite/gcc.dg/pr103431.c
new file mode 100644
index 0000000..09f224a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr103431.c
@@ -0,0 +1,21 @@
+/* PR middle-end/103431 */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-O -fno-tree-bit-ccp -fno-tree-dominator-opts" } */
+
+__attribute__((noipa))
+void foo (unsigned short a)
+{
+  __uint128_t b = 5;
+  int size = __SIZEOF_INT128__ * __CHAR_BIT__ - 1;
+  a /= 0xfffffffd;
+  __uint128_t c = (b << (a & size) | b >> (-(a & size) & size));
+  if (c != 5)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+  foo (0);
+  return 0;
+}