[llvm] [CodeGenPrepare] Replace deleted sext instr with the promoted value. (PR #71058)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Yingwei Zheng (dtcxzyw)

<details>
<summary>Changes</summary>

This PR replaces the deleted sext with the promoted value in `AddrMode`.
Fixes #<!-- -->70938.

---
Full diff: https://github.com/llvm/llvm-project/pull/71058.diff


2 Files Affected:

- (modified) llvm/lib/CodeGen/CodeGenPrepare.cpp (+12) 
- (modified) llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll (+22) 


``````````diff
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 187820717b6fd5c..9018b87835b775f 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -2634,6 +2634,15 @@ struct ExtAddrMode : public TargetLowering::AddrMode {
   void print(raw_ostream &OS) const;
   void dump() const;
 
+  void replaceWith(Value *From, Value *To) {
+    if (BaseReg == From)
+      BaseReg = To;
+    if (ScaledReg == From)
+      ScaledReg = To;
+    if (OriginalValue == From)
+      OriginalValue = 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.
@@ -4933,6 +4942,9 @@ 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;
   }
   }
diff --git a/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll b/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
index 6e95c91e7398932..a7f6f803d58fd4c 100644
--- a/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
+++ b/llvm/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
@@ -507,3 +507,25 @@ 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.
+; CHECK-LABEL: define void @pr70938(
+; CHECK-SAME: ptr [[F:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 0, 0
+; CHECK-NEXT:    [[SUNKADDR:%.*]] = mul i64 [[ADD]], 2
+; CHECK-NEXT:    [[SUNKADDR1:%.*]] = getelementptr i8, ptr [[F]], i64 [[SUNKADDR]]
+; CHECK-NEXT:    store i8 0, ptr [[SUNKADDR1]], align 1
+; CHECK-NEXT:    ret void
+define void @pr70938(ptr %f) {
+entry:
+  %add = add nsw i32 0, 0
+  %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
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/71058