MSP430: sim: Fix incorrect simulation of unsigned widening multiply

Operand sizes used for simulation of MSP430 hardware multiply
operations are not aligned with the sizes used on the target, resulting
in the simulator storing signed operands with too much precision.

Additionally, simulation of unsigned multiplication is missing explicit
casts to prevent any implicit sign extension.

gcc.c-torture/execute/pr91450-1.c uses unsigned widening multiplication
of 32-bit operands -4 and 2, to produce a 64-bit result:
0xffff fffc * 0x2 = 0x1 ffff fff8

If -4 is stored in 64-bit precision, then the multiplication is
essentially signed and the result is -8 in 64-bit precision
(0xffff ffff ffff fffc), which is not correct.

sim/msp430/ChangeLog:

	* msp430-sim.c (put_op): For unsigned multiplication, explicitly cast
	operands to the unsigned type before multiplying.
	* msp430-sim.h (struct msp430_cpu_state): Fix types used to store hwmult
	operands.

sim/testsuite/sim/msp430/ChangeLog:

	* mpyull_hwmult.s: New test.

3 files changed, 31 insertions, 12 deletions

diff --git a/sim/msp430/ChangeLog b/sim/msp430/ChangeLog
index 0f27982..41da2a7 100644
--- a/sim/msp430/ChangeLog
+++ b/sim/msp430/ChangeLog
@@ -1,3 +1,10 @@
+2020-08-05  Jozef Lawrynowicz  <jozef.l@mittosystems.com>
+
+	* msp430-sim.c (put_op): For unsigned multiplication, explicitly cast
+	operands to the unsigned type before multiplying.
+	* msp430-sim.h (struct msp430_cpu_state): Fix types used to store hwmult
+	operands.
+
 2020-01-22  Jozef Lawrynowicz  <jozef.l@mittosystems.com>
 
 	* msp430-sim.c (msp430_step_once): Ignore the carry flag when executing
diff --git a/sim/msp430/msp430-sim.c b/sim/msp430/msp430-sim.c
index e21c8cf..a330c6c 100644
--- a/sim/msp430/msp430-sim.c
+++ b/sim/msp430/msp430-sim.c
@@ -566,8 +566,13 @@ put_op (SIM_DESC sd, MSP430_Opcode_Decoded *opc, int n, int val)
 	      switch (HWMULT (sd, hwmult_type))
 		{
 		case UNSIGN_32:
-		  HWMULT (sd, hwmult_result) = HWMULT (sd, hwmult_op1) * HWMULT (sd, hwmult_op2);
-		  HWMULT (sd, hwmult_signed_result) = (signed) HWMULT (sd, hwmult_result);
+		  a = HWMULT (sd, hwmult_op1);
+		  b = HWMULT (sd, hwmult_op2);
+		  /* For unsigned 32-bit multiplication of 16-bit operands, an
+		     explicit cast is required to prevent any implicit
+		     sign-extension.  */
+		  HWMULT (sd, hwmult_result) = (unsigned32) a * (unsigned32) b;
+		  HWMULT (sd, hwmult_signed_result) = a * b;
 		  HWMULT (sd, hwmult_accumulator) = HWMULT (sd, hwmult_signed_accumulator) = 0;
 		  break;
 
@@ -575,13 +580,16 @@ put_op (SIM_DESC sd, MSP430_Opcode_Decoded *opc, int n, int val)
 		  a = sign_ext (HWMULT (sd, hwmult_op1), 16);
 		  b = sign_ext (HWMULT (sd, hwmult_op2), 16);
 		  HWMULT (sd, hwmult_signed_result) = a * b;
-		  HWMULT (sd, hwmult_result) = (unsigned) HWMULT (sd, hwmult_signed_result);
+		  HWMULT (sd, hwmult_result) = (unsigned32) a * (unsigned32) b;
 		  HWMULT (sd, hwmult_accumulator) = HWMULT (sd, hwmult_signed_accumulator) = 0;
 		  break;
 
 		case UNSIGN_MAC_32:
-		  HWMULT (sd, hwmult_accumulator) += HWMULT (sd, hwmult_op1) * HWMULT (sd, hwmult_op2);
-		  HWMULT (sd, hwmult_signed_accumulator) += HWMULT (sd, hwmult_op1) * HWMULT (sd, hwmult_op2);
+		  a = HWMULT (sd, hwmult_op1);
+		  b = HWMULT (sd, hwmult_op2);
+		  HWMULT (sd, hwmult_accumulator)
+		    += (unsigned32) a * (unsigned32) b;
+		  HWMULT (sd, hwmult_signed_accumulator) += a * b;
 		  HWMULT (sd, hwmult_result) = HWMULT (sd, hwmult_accumulator);
 		  HWMULT (sd, hwmult_signed_result) = HWMULT (sd, hwmult_signed_accumulator);
 		  break;
@@ -589,7 +597,8 @@ put_op (SIM_DESC sd, MSP430_Opcode_Decoded *opc, int n, int val)
 		case SIGN_MAC_32:
 		  a = sign_ext (HWMULT (sd, hwmult_op1), 16);
 		  b = sign_ext (HWMULT (sd, hwmult_op2), 16);
-		  HWMULT (sd, hwmult_accumulator) += a * b;
+		  HWMULT (sd, hwmult_accumulator)
+		    += (unsigned32) a * (unsigned32) b;
 		  HWMULT (sd, hwmult_signed_accumulator) += a * b;
 		  HWMULT (sd, hwmult_result) = HWMULT (sd, hwmult_accumulator);
 		  HWMULT (sd, hwmult_signed_result) = HWMULT (sd, hwmult_signed_accumulator);
@@ -648,10 +657,13 @@ put_op (SIM_DESC sd, MSP430_Opcode_Decoded *opc, int n, int val)
 	      switch (HWMULT (sd, hw32mult_type))
 		{
 		case UNSIGN_64:
-		  HWMULT (sd, hw32mult_result) = HWMULT (sd, hw32mult_op1) * HWMULT (sd, hw32mult_op2);
+		  HWMULT (sd, hw32mult_result)
+		    = (unsigned64) HWMULT (sd, hw32mult_op1)
+		    * (unsigned64) HWMULT (sd, hw32mult_op2);
 		  break;
 		case SIGN_64:
-		  HWMULT (sd, hw32mult_result) = sign_ext (HWMULT (sd, hw32mult_op1), 32)
+		  HWMULT (sd, hw32mult_result)
+		    = sign_ext (HWMULT (sd, hw32mult_op1), 32)
 		    * sign_ext (HWMULT (sd, hw32mult_op2), 32);
 		  break;
 		}
diff --git a/sim/msp430/msp430-sim.h b/sim/msp430/msp430-sim.h
index ad83e5b..7c486c2 100644
--- a/sim/msp430/msp430-sim.h
+++ b/sim/msp430/msp430-sim.h
@@ -31,16 +31,16 @@ struct msp430_cpu_state
   int cio_buffer;
 
   hwmult_type  hwmult_type;
-  unsigned32   hwmult_op1;
-  unsigned32   hwmult_op2;
+  unsigned16   hwmult_op1;
+  unsigned16   hwmult_op2;
   unsigned32   hwmult_result;
   signed32     hwmult_signed_result;
   unsigned32   hwmult_accumulator;
   signed32     hwmult_signed_accumulator;
 
   hw32mult_type  hw32mult_type;
-  unsigned64     hw32mult_op1;
-  unsigned64     hw32mult_op2;
+  unsigned32     hw32mult_op1;
+  unsigned32     hw32mult_op2;
   unsigned64     hw32mult_result;
 };