[PATCH] D98145: [FastISel] Don't trivially kill extractvalues (PR49467)

[Nikita Popov via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG55ae279ba7a5: [FastISel] Don't trivially kill extractvalues (PR49467) (authored by nikic).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D98145/new/

https://reviews.llvm.org/D98145

Files:
  llvm/include/llvm/CodeGen/FastISel.h
  llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
  llvm/test/CodeGen/X86/pr49467.ll


Index: llvm/test/CodeGen/X86/pr49467.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/pr49467.ll
@@ -0,0 +1,27 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -O0 -fast-isel -verify-machineinstrs -mtriple=x86_64 < %s | FileCheck %s
+
+declare { i8*, i64 } @get()
+
+declare void @use(i8*, i64)
+
+define void @test(i64* %p) nounwind {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    movq %rdi, (%rsp) # 8-byte Spill
+; CHECK-NEXT:    callq get at PLT
+; CHECK-NEXT:    movq (%rsp), %rdi # 8-byte Reload
+; CHECK-NEXT:    movq %rdx, %rsi
+; CHECK-NEXT:    movq %rsi, (%rdi)
+; CHECK-NEXT:    # implicit-def: $rdi
+; CHECK-NEXT:    callq use at PLT
+; CHECK-NEXT:    popq %rax
+; CHECK-NEXT:    retq
+  %struct = call { i8*, i64 } @get()
+  %struct.1 = extractvalue { i8*, i64 } %struct, 1
+  store i64 %struct.1, i64* %p, align 8
+  %struct.2 = extractvalue { i8*, i64 } %struct, 1
+  call void @use(i8* undef, i64 %struct.2)
+  ret void
+}
Index: llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -261,12 +261,16 @@
     if (GEP->hasAllZeroIndices() && !hasTrivialKill(GEP->getOperand(0)))
       return false;
 
+  // Casts and extractvalues may be trivially coalesced by fast-isel.
+  if (I->getOpcode() == Instruction::BitCast ||
+      I->getOpcode() == Instruction::PtrToInt ||
+      I->getOpcode() == Instruction::IntToPtr ||
+      I->getOpcode() == Instruction::ExtractValue)
+    return false;
+
   // Only instructions with a single use in the same basic block are considered
   // to have trivial kills.
   return I->hasOneUse() &&
-         !(I->getOpcode() == Instruction::BitCast ||
-           I->getOpcode() == Instruction::PtrToInt ||
-           I->getOpcode() == Instruction::IntToPtr) &&
          cast<Instruction>(*I->user_begin())->getParent() == I->getParent();
 }
 
Index: llvm/include/llvm/CodeGen/FastISel.h
===================================================================
--- llvm/include/llvm/CodeGen/FastISel.h
+++ llvm/include/llvm/CodeGen/FastISel.h
@@ -490,7 +490,10 @@
   /// - \c Add has a constant operand.
   bool canFoldAddIntoGEP(const User *GEP, const Value *Add);
 
-  /// Test whether the given value has exactly one use.
+  /// Test whether the register associated with this value has exactly one use,
+  /// in which case that single use is killing. Note that multiple IR values
+  /// may map onto the same register, in which case this is not the same as
+  /// checking that an IR value has one use.
   bool hasTrivialKill(const Value *V);
 
   /// Create a machine mem operand from the given instruction.


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