[clang] Desugar complex element types for promoted complex division (PR #168943)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

Author: Zahira Ammarguellat (zahiraam)

<details>
<summary>Changes</summary>

This patch fixes a crash in Clang that occurs when the compiler retrieves the element type of a complex type but receives a sugared type. See example here: https://godbolt.org/z/cdbdeMcaT 
This patch fixes the crash.

---
Full diff: https://github.com/llvm/llvm-project/pull/168943.diff


3 Files Affected:

- (modified) clang/lib/CodeGen/CGExprComplex.cpp (+2-1) 
- (modified) clang/lib/Sema/SemaExpr.cpp (+2-2) 
- (modified) clang/test/CodeGen/promoted-complex-div.c (+52) 


``````````diff
diff --git a/clang/lib/CodeGen/CGExprComplex.cpp b/clang/lib/CodeGen/CGExprComplex.cpp
index d281c4c20616a..f33e5d75296eb 100644
--- a/clang/lib/CodeGen/CGExprComplex.cpp
+++ b/clang/lib/CodeGen/CGExprComplex.cpp
@@ -320,7 +320,8 @@ class ComplexExprEmitter
   QualType getPromotionType(FPOptionsOverride Features, QualType Ty,
                             bool IsComplexDivisor) {
     if (auto *CT = Ty->getAs<ComplexType>()) {
-      QualType ElementType = CT->getElementType();
+      QualType ElementType =
+          CT->getElementType().getDesugaredType(CGF.getContext());
       bool IsFloatingType = ElementType->isFloatingType();
       bool IsComplexRangePromoted = CGF.getLangOpts().getComplexRange() ==
                                     LangOptions::ComplexRangeKind::CX_Promoted;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 10f0ec3010c6c..ea7937d551ddb 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -10726,13 +10726,13 @@ static void DetectPrecisionLossInComplexDivision(Sema &S, QualType DivisorTy,
   if (!CT)
     return;
 
-  QualType ElementType = CT->getElementType();
+  ASTContext &Ctx = S.getASTContext();
+  QualType ElementType = CT->getElementType().getDesugaredType(Ctx);
   bool IsComplexRangePromoted = S.getLangOpts().getComplexRange() ==
                                 LangOptions::ComplexRangeKind::CX_Promoted;
   if (!ElementType->isFloatingType() || !IsComplexRangePromoted)
     return;
 
-  ASTContext &Ctx = S.getASTContext();
   QualType HigherElementType = Ctx.GetHigherPrecisionFPType(ElementType);
   const llvm::fltSemantics &ElementTypeSemantics =
       Ctx.getFloatTypeSemantics(ElementType);
diff --git a/clang/test/CodeGen/promoted-complex-div.c b/clang/test/CodeGen/promoted-complex-div.c
index 7ed7b07db83ae..006b5e334e6ea 100644
--- a/clang/test/CodeGen/promoted-complex-div.c
+++ b/clang/test/CodeGen/promoted-complex-div.c
@@ -81,3 +81,55 @@ _Complex double divf(_Complex double a, _Complex double b) {
 
   return a / b; // nopromotion-warning{{excess precision is requested but the target does not support excess precision which may result in observable differences in complex division behavior}}
 }
+
+// This test ensures that Clang does not crash when complex element types
+// require desugaring under -complex-range=promoted. Previously, a sugared
+// typedef element type (e.g., 'typedef double a') caused a crash during
+// complex range evaluation in both Sema and CodeGen.
+typedef double a;
+_Complex double *b;
+// CHECK-LABEL: define dso_local void @DivideByComplexZero
+void DivideByComplexZero() {
+  // CHECK: fpext double {{.*}} to x86_fp80
+  // CHECK: fpext double {{.*}} to x86_fp80
+  // CHECK: fmul x86_fp80
+  // CHECK: fmul x86_fp80
+  // CHECK: fadd x86_fp80
+  // CHECK: fmul x86_fp80
+  // CHECK: fmul x86_fp80
+  // CHECK: fsub x86_fp80
+  // CHECK: fdiv x86_fp80
+  // CHECK: fdiv x86_fp80
+  // CHECK: fptrunc x86_fp80
+  // CHECK: fptrunc x86_fp80
+
+  // NOX87: call double @llvm.fabs.f64(double {{.*}})
+  // NOX87-NEXT: call double @llvm.fabs.f64(double {{.*}}
+  // NOX87-NEXT: fcmp ugt double {{.*}}, {{.*}}
+  // NOX87-NEXT: br i1 {{.*}}, label
+  // NOX87: abs_rhsr_greater_or_equal_abs_rhsi:
+  // NOX87-NEXT: fmul double
+  // NOX87-NEXT: fadd double
+  // NOX87-NEXT: fdiv double
+  // NOX87-NEXT: fmul double
+  // NOX87-NEXT: fsub double
+  // NOX87-NEXT: fdiv double
+  // NOX87-NEXT: br label {{.*}}
+  // NOX87: abs_rhsr_less_than_abs_rhsi:
+  // NOX87-NEXT: fmul double
+  // NOX87-NEXT: fadd double
+  // NOX87-NEXT: fdiv double
+  // NOX87-NEXT: fmul double
+  // NOX87-NEXT: fsub double
+  // NOX87-NEXT: fdiv double
+  // NOX87-NEXT: br label {{.*}}
+  // NOX87: complex_div:
+  // NOX87-NEXT: phi double
+  // NOX87-NEXT: phi double
+  // NOX87-NEXT: getelementptr inbounds nuw { double, double }, ptr {{.*}}, i32 0, i32 0
+  // NOX87-NEXT: getelementptr inbounds nuw { double, double }, ptr {{.*}}, i32 0, i32 1
+  // NOX87-NEXT: store double
+  // NOX87-NEXT: store double
+
+  *b /= 1.0iF * (a)0;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/168943