release/20.x: [CodeGenPrepare] Replace deleted ext instr with the promoted value. (#71058)

[llvmbot]

Backport 3c6aa04

Requested by: @nikic

[llvmbot]

@nikic What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: None (llvmbot)

Changes

Backport 3c6aa04

Requested by: @nikic

---

Full diff: https://github.com/llvm/llvm-project/pull/125040.diff

2 Files Affected:

• (modified) llvm/lib/CodeGen/CodeGenPrepare.cpp (+11)
• (modified) llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll (+48)

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 47486a30bba5ba..088062afab177d 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -3074,6 +3074,14 @@ struct ExtAddrMode : public TargetLowering::AddrMode {
   void print(raw_ostream &OS) const;
   void dump() const;
 
+  // Replace From in ExtAddrMode with To.
+  // E.g., SExt insts may be promoted and deleted. We should replace them with
+  // the promoted values.
+  void replaceWith(Value *From, Value *To) {
+    if (ScaledReg == From)
+      ScaledReg = To;
+  }
+
   FieldName compare(const ExtAddrMode &other) {
     // First check that the types are the same on each field, as differing types
     // is something we can't cope with later on.
@@ -5365,6 +5373,9 @@ bool AddressingModeMatcher::matchOperationAddr(User *AddrInst, unsigned Opcode,
       TPT.rollback(LastKnownGood);
       return false;
     }
+
+    // SExt has been deleted. Make sure it is not referenced by the AddrMode.
+    AddrMode.replaceWith(Ext, PromotedOperand);
     return true;
   }
   case Instruction::Call:
diff --git a/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll b/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
index f3070cd55903bd..9755916f823789 100644
--- a/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
+++ b/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
@@ -620,3 +620,51 @@ define i8 @oneArgPromotionBlockSExtZExt(i1 %arg1, ptr %base) {
   %res = load i8, ptr %arrayidx
   ret i8 %res
 }
+
+; Check that we replace the deleted sext with the promoted value.
+define void @pr70938(ptr %f) {
+; CHECK-LABEL: define void @pr70938(
+; CHECK-SAME: ptr [[F:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 0, 1
+; CHECK-NEXT:    [[SUNKADDR:%.*]] = mul i64 [[ADD]], 2
+; CHECK-NEXT:    [[SUNKADDR1:%.*]] = getelementptr i8, ptr [[F]], i64 [[SUNKADDR]]
+; CHECK-NEXT:    [[SUNKADDR2:%.*]] = getelementptr i8, ptr [[SUNKADDR1]], i64 1
+; CHECK-NEXT:    store i8 0, ptr [[SUNKADDR2]], align 1
+; CHECK-NEXT:    ret void
+;
+entry:
+  %add = add nsw i32 0, 1
+  %idxprom3 = sext i32 %add to i64
+  %arrayidx4 = getelementptr [2 x [1 x [2 x i8]]], ptr %f, i64 0, i64 %idxprom3
+  %arrayidx8 = getelementptr [2 x i8], ptr %arrayidx4, i64 0, i64 %idxprom3
+  br label %if.end
+
+if.end:                                           ; preds = %entry
+  store i8 0, ptr %arrayidx8, align 1
+  ret void
+}
+
+define void @pr119429() {
+; CHECK-LABEL: define void @pr119429() {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[AND:%.*]] = and i64 0, 0
+; CHECK-NEXT:    [[SUNKADDR:%.*]] = inttoptr i64 [[AND]] to ptr
+; CHECK-NEXT:    [[SUNKADDR1:%.*]] = mul i64 [[AND]], 2
+; CHECK-NEXT:    [[SUNKADDR2:%.*]] = getelementptr i8, ptr [[SUNKADDR]], i64 [[SUNKADDR1]]
+; CHECK-NEXT:    store i64 0, ptr [[SUNKADDR2]], align 8
+; CHECK-NEXT:    ret void
+;
+entry:
+  %and = and i32 0, 0
+  %conv1 = zext i32 %and to i64
+  %sub = add i64 %conv1, 0
+  br label %if.end
+
+if.end:
+  %mul = shl i64 %sub, 1
+  %add = add i64 %mul, %conv1
+  %ptr = inttoptr i64 %add to ptr
+  store i64 0, ptr %ptr, align 8
+  ret void
+}

[github-actions]

@nikic (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.