[llvm] 6588ac3 - [MachineCombiner] Don't ignore PHI depths (#82025)

[via llvm-commits]

Author: Jonas Paulsson
Date: 2024-03-14T11:47:29-04:00
New Revision: 6588ac3017df0095b160510f56dcb3e4c32a09f0

URL: https://github.com/llvm/llvm-project/commit/6588ac3017df0095b160510f56dcb3e4c32a09f0
DIFF: https://github.com/llvm/llvm-project/commit/6588ac3017df0095b160510f56dcb3e4c32a09f0.diff

LOG: [MachineCombiner] Don't ignore PHI depths (#82025)

The depths of the Root and the NewRoot are to be compared in
MachineCombiner::improvesCriticalPathLen(), and while the call to
BlockTrace.getInstrCycles(*Root) includes the Depth of a PHI, for some
reason PHI nodes have been ignored in getOperandDef(). 

This patch removes the special handling of PHIs in getOperandDef() so that
Root and NewRoot get a fair comparison. This does not affect loop headers
as MachineTraceMetrics handles that case by ignoring incoming PHI edges.

Added: 
    

Modified: 
    llvm/lib/CodeGen/MachineCombiner.cpp
    llvm/test/CodeGen/RISCV/umulo-128-legalisation-lowering.ll
    llvm/test/CodeGen/X86/bitcast-and-setcc-256.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/MachineCombiner.cpp b/llvm/lib/CodeGen/MachineCombiner.cpp
index c65937935ed820..a4c87a7678bd8d 100644
--- a/llvm/lib/CodeGen/MachineCombiner.cpp
+++ b/llvm/lib/CodeGen/MachineCombiner.cpp
@@ -155,9 +155,6 @@ MachineCombiner::getOperandDef(const MachineOperand &MO) {
   // We need a virtual register definition.
   if (MO.isReg() && MO.getReg().isVirtual())
     DefInstr = MRI->getUniqueVRegDef(MO.getReg());
-  // PHI's have no depth etc.
-  if (DefInstr && DefInstr->isPHI())
-    DefInstr = nullptr;
   return DefInstr;
 }
 

diff  --git a/llvm/test/CodeGen/RISCV/umulo-128-legalisation-lowering.ll b/llvm/test/CodeGen/RISCV/umulo-128-legalisation-lowering.ll
index 8c0d97afe6c21d..f1ae3200175636 100644
--- a/llvm/test/CodeGen/RISCV/umulo-128-legalisation-lowering.ll
+++ b/llvm/test/CodeGen/RISCV/umulo-128-legalisation-lowering.ll
@@ -89,8 +89,8 @@ define { i128, i8 } @muloti_test(i128 %l, i128 %r) #0 {
 ; RISCV32-NEXT:    snez a3, a3
 ; RISCV32-NEXT:    and a3, a3, a7
 ; RISCV32-NEXT:    or a2, a3, a2
-; RISCV32-NEXT:    or a3, t2, t3
-; RISCV32-NEXT:    or a2, a2, a3
+; RISCV32-NEXT:    or a2, a2, t2
+; RISCV32-NEXT:    or a2, a2, t3
 ; RISCV32-NEXT:    mul a3, a5, a4
 ; RISCV32-NEXT:    andi a2, a2, 1
 ; RISCV32-NEXT:    sw a3, 0(a0)

diff  --git a/llvm/test/CodeGen/X86/bitcast-and-setcc-256.ll b/llvm/test/CodeGen/X86/bitcast-and-setcc-256.ll
index 34ef23db345755..234c7a0a500d30 100644
--- a/llvm/test/CodeGen/X86/bitcast-and-setcc-256.ll
+++ b/llvm/test/CodeGen/X86/bitcast-and-setcc-256.ll
@@ -553,8 +553,8 @@ define i8 @v8i32_or_select(<8 x i32> %a0, <8 x i32> %a1, <8 x i32> %a2, <8 x i32
 ; AVX1-NEXT:    vpcmpeqd %xmm5, %xmm4, %xmm4
 ; AVX1-NEXT:    vpcmpeqd %xmm1, %xmm0, %xmm0
 ; AVX1-NEXT:    vinsertf128 $1, %xmm4, %ymm0, %ymm0
-; AVX1-NEXT:    vorps %ymm2, %ymm3, %ymm1
-; AVX1-NEXT:    vorps %ymm0, %ymm1, %ymm0
+; AVX1-NEXT:    vorps %ymm0, %ymm3, %ymm0
+; AVX1-NEXT:    vorps %ymm2, %ymm0, %ymm0
 ; AVX1-NEXT:    vmovmskps %ymm0, %eax
 ; AVX1-NEXT:    # kill: def $al killed $al killed $eax
 ; AVX1-NEXT:    vzeroupper
@@ -571,8 +571,8 @@ define i8 @v8i32_or_select(<8 x i32> %a0, <8 x i32> %a1, <8 x i32> %a2, <8 x i32
 ; AVX2-NEXT:    vpcmpeqd %ymm2, %ymm0, %ymm2
 ; AVX2-NEXT:  .LBB7_3:
 ; AVX2-NEXT:    vpcmpeqd %ymm1, %ymm0, %ymm0
-; AVX2-NEXT:    vpor %ymm2, %ymm3, %ymm1
-; AVX2-NEXT:    vpor %ymm0, %ymm1, %ymm0
+; AVX2-NEXT:    vpor %ymm0, %ymm3, %ymm0
+; AVX2-NEXT:    vpor %ymm2, %ymm0, %ymm0
 ; AVX2-NEXT:    vmovmskps %ymm0, %eax
 ; AVX2-NEXT:    # kill: def $al killed $al killed $eax
 ; AVX2-NEXT:    vzeroupper