Fix complex long double division with -mno-x87. (#133152)

The combination of `-fcomplex-arithmetic=promoted` and `mno-x87` for
`double` complex division is leading to a crash.
See https://godbolt.org/z/189G957oY
This patch fixes that.

Author: zahiraam

clang/lib/CodeGen/CGExprComplex.cpp

@@ -303,6 +303,10 @@ class ComplexExprEmitter
     // doubles the exponent of SmallerType.LargestFiniteVal)
     if (llvm::APFloat::semanticsMaxExponent(ElementTypeSemantics) * 2 + 1 <=
         llvm::APFloat::semanticsMaxExponent(HigherElementTypeSemantics)) {
+      if (!Ctx.getTargetInfo().hasLongDoubleType() &&
+          HigherElementType.getCanonicalType().getUnqualifiedType() ==
+              Ctx.LongDoubleTy)
+        return QualType();
       FPHasBeenPromoted = true;
       return Ctx.getComplexType(HigherElementType);
     } else {

clang/lib/Sema/SemaExpr.cpp

@@ -15329,8 +15329,10 @@ static void DetectPrecisionLossInComplexDivision(Sema &S, SourceLocation OpLoc,
           Ctx.getFloatTypeSemantics(ElementType);
       const llvm::fltSemantics &HigherElementTypeSemantics =
           Ctx.getFloatTypeSemantics(HigherElementType);
-      if (llvm::APFloat::semanticsMaxExponent(ElementTypeSemantics) * 2 + 1 >
-          llvm::APFloat::semanticsMaxExponent(HigherElementTypeSemantics)) {
+      if ((llvm::APFloat::semanticsMaxExponent(ElementTypeSemantics) * 2 + 1 >
+           llvm::APFloat::semanticsMaxExponent(HigherElementTypeSemantics)) ||
+          (HigherElementType == Ctx.LongDoubleTy &&
+           !Ctx.getTargetInfo().hasLongDoubleType())) {
         // Retain the location of the first use of higher precision type.
         if (!S.LocationOfExcessPrecisionNotSatisfied.isValid())
           S.LocationOfExcessPrecisionNotSatisfied = OpLoc;

clang/test/CodeGen/promoted-complex-div.c

@@ -0,0 +1,83 @@
+// RUN: %clang_cc1 %s -O0 -emit-llvm -triple x86_64-unknown-unknown \
+// RUN: -verify -complex-range=promoted -o - | FileCheck %s
+
+// RUN: %clang_cc1 %s -O0 -emit-llvm -triple x86_64-unknown-unknown \
+// RUN: -verify=nopromotion -complex-range=promoted -target-feature -x87 \
+// RUN: -o - | FileCheck %s --check-prefix=NOX87
+
+// RUN: %clang_cc1 %s -O0 -emit-llvm -triple x86_64-unknown-windows \
+// RUN: -verify=nopromotion -complex-range=promoted -o - \
+// RUN: | FileCheck %s --check-prefix=NOX87
+
+// RUN: %clang_cc1 %s -O0 -emit-llvm -triple x86_64-unknown-windows \
+// RUN: -verify=nopromotion -complex-range=promoted -target-feature -x87 \
+// RUN: -o - | FileCheck %s --check-prefix=NOX87
+
+
+
+// expected-no-diagnostics
+
+// CHECK-LABEL: define dso_local <2 x float> @divd
+_Complex float divd(_Complex float a, _Complex float b) {
+  // CHECK: fpext float {{.*}} to double
+  // CHECK: fpext float {{.*}} to double
+  // CHECK: fdiv double
+  // CHECK: fdiv double
+  // CHECK: fptrunc double {{.*}} to float
+  // CHECK: fptrunc double {{.*}} to float
+
+  // NOX87: fpext float {{.*}} to double
+  // NOX87: fpext float {{.*}} to double
+  // NOX87: fdiv double
+  // NOX87: fdiv double
+  // NOX87: fptrunc double {{.*}} to float
+  // NOX87: fptrunc double {{.*}} to float
+
+  return a / b;
+}
+
+// CHECK-LABEL: define dso_local { double, double } @divf
+_Complex double divf(_Complex double a, _Complex double b) {
+  // CHECK: fpext double {{.*}} to x86_fp80
+  // CHECK: fpext double {{.*}} to 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: fdiv double
+  // NOX87-NEXT: fmul double
+  // NOX87-NEXT: fadd double
+  // 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: fdiv double
+  // NOX87-NEXT: fmul double
+  // NOX87-NEXT: fadd double
+  // 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
+
+  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}}
+}