[PATCH] D81875: [GlobalISel] Look through extends etc in CombinerHelper::matchConstantOp

[Jessica Paquette via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG5a4c3f6b06f6: [GlobalISel] Look through extends etc in CombinerHelper::matchConstantOp (authored by paquette).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D81875/new/

https://reviews.llvm.org/D81875

Files:
  llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-trivial-arith.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-trivial-arith.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-trivial-arith.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-trivial-arith.mir
@@ -286,4 +286,24 @@
     %op:_(s32) = G_SUB %x(s32), %cst
     $w0 = COPY %op(s32)
     RET_ReallyLR implicit $w0
+
+...
+---
+name:            look_through_zext
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x0
+    ; CHECK-LABEL: name: look_through_zext
+    ; CHECK: liveins: $x0
+    ; CHECK: %zero:_(s8) = G_CONSTANT i8 0
+    ; CHECK: %zext_zero:_(s64) = G_ZEXT %zero(s8)
+    ; CHECK: $x0 = COPY %zext_zero(s64)
+    ; CHECK: RET_ReallyLR implicit $x0
+    %zero:_(s8) = G_CONSTANT i8 0
+    %zext_zero:_(s64) = G_ZEXT %zero(s8)
+    %c:_(s64) = G_CONSTANT i64 72340172838076673
+    %mul:_(s64) = G_MUL %c, %zext_zero
+    $x0 = COPY %mul(s64)
+    RET_ReallyLR implicit $x0
 ...
Index: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -1617,8 +1617,9 @@
 bool CombinerHelper::matchConstantOp(const MachineOperand &MOP, int64_t C) {
   if (!MOP.isReg())
     return false;
-  int64_t Cst;
-  return mi_match(MOP.getReg(), MRI, m_ICst(Cst)) && Cst == C;
+  // MIPatternMatch doesn't let us look through G_ZEXT etc.
+  auto ValAndVReg = getConstantVRegValWithLookThrough(MOP.getReg(), MRI);
+  return ValAndVReg && ValAndVReg->Value == C;
 }
 
 bool CombinerHelper::replaceSingleDefInstWithOperand(MachineInstr &MI,


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