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| author | Roger Sayle <roger@nextmovesoftware.com> | 2023-10-26 10:06:59 +0100 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2023-10-26 10:06:59 +0100 |
| commit | d1bb9569d7030490fe7bb35af432f934560d689d (patch) | |
| tree | 4b1c1b849e656e9089917d3ca9bd483837236876 | |
| parent | 2f592b7b55b545ea4e3bd4fe88fc8d6fbfa3c5a5 (diff) | |
| download | gcc-d1bb9569d7030490fe7bb35af432f934560d689d.zip gcc-d1bb9569d7030490fe7bb35af432f934560d689d.tar.gz gcc-d1bb9569d7030490fe7bb35af432f934560d689d.tar.bz2 | |
PR 91865: Avoid ZERO_EXTEND of ZERO_EXTEND in make_compound_operation.
This patch is my proposed solution to PR rtl-optimization/91865.
Normally RTX simplification canonicalizes a ZERO_EXTEND of a ZERO_EXTEND
to a single ZERO_EXTEND, but as shown in this PR it is possible for
combine's make_compound_operation to unintentionally generate a
non-canonical ZERO_EXTEND of a ZERO_EXTEND, which is unlikely to be
matched by the backend.
For the new test case:
const int table[2] = {1, 2};
int foo (char i) { return table[i]; }
compiling with -O2 -mlarge on msp430 we currently see:
Trying 2 -> 7:
2: r25:HI=zero_extend(R12:QI)
REG_DEAD R12:QI
7: r28:PSI=sign_extend(r25:HI)#0
REG_DEAD r25:HI
Failed to match this instruction:
(set (reg:PSI 28 [ iD.1772 ])
(zero_extend:PSI (zero_extend:HI (reg:QI 12 R12 [ iD.1772 ]))))
which results in the following code:
foo: AND #0xff, R12
RLAM.A #4, R12 { RRAM.A #4, R12
RLAM.A #1, R12
MOVX.W table(R12), R12
RETA
With this patch, we now see:
Trying 2 -> 7:
2: r25:HI=zero_extend(R12:QI)
REG_DEAD R12:QI
7: r28:PSI=sign_extend(r25:HI)#0
REG_DEAD r25:HI
Successfully matched this instruction:
(set (reg:PSI 28 [ iD.1772 ])
(zero_extend:PSI (reg:QI 12 R12 [ iD.1772 ])))
allowing combination of insns 2 and 7
original costs 4 + 8 = 12
replacement cost 8
foo: MOV.B R12, R12
RLAM.A #1, R12
MOVX.W table(R12), R12
RETA
2023-10-26 Roger Sayle <roger@nextmovesoftware.com>
Richard Biener <rguenther@suse.de>
gcc/ChangeLog
PR rtl-optimization/91865
* combine.cc (make_compound_operation): Avoid creating a
ZERO_EXTEND of a ZERO_EXTEND.
gcc/testsuite/ChangeLog
PR rtl-optimization/91865
* gcc.target/msp430/pr91865.c: New test case.
| -rw-r--r-- | gcc/combine.cc | 4 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.target/msp430/pr91865.c | 8 |
2 files changed, 10 insertions, 2 deletions
diff --git a/gcc/combine.cc b/gcc/combine.cc index cb48e7f..6344cd3 100644 --- a/gcc/combine.cc +++ b/gcc/combine.cc @@ -8449,8 +8449,8 @@ make_compound_operation (rtx x, enum rtx_code in_code) if (code == ZERO_EXTEND) { new_rtx = make_compound_operation (XEXP (x, 0), next_code); - tem = simplify_const_unary_operation (ZERO_EXTEND, GET_MODE (x), - new_rtx, GET_MODE (XEXP (x, 0))); + tem = simplify_unary_operation (ZERO_EXTEND, GET_MODE (x), + new_rtx, GET_MODE (XEXP (x, 0))); if (tem) return tem; SUBST (XEXP (x, 0), new_rtx); diff --git a/gcc/testsuite/gcc.target/msp430/pr91865.c b/gcc/testsuite/gcc.target/msp430/pr91865.c new file mode 100644 index 0000000..8cc21c8 --- /dev/null +++ b/gcc/testsuite/gcc.target/msp430/pr91865.c @@ -0,0 +1,8 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -mlarge" } */ + +const int table[2] = {1, 2}; +int foo (char i) { return table[i]; } + +/* { dg-final { scan-assembler-not "AND" } } */ +/* { dg-final { scan-assembler-not "RRAM" } } */ |