3b25407d97
Introduce isDesirableCastOp() which determines whether IR builder and constant folding should produce constant expressions for a given cast type. This mirrors what we do for binary operators. Mark zext/sext as undesirable, which prevents most creations of such constant expressions. This is still somewhat incomplete and there are a few more places that can create zext/sext expressions. This is part of the work for https://discourse.llvm.org/t/rfc-remove-most-constant-expressions/63179. The reason for the odd result in the constantexpr-fneg.c test is that initially the "a[]" global is created with an [0 x i32] type, at which point the icmp expression cannot be folded. Later it is replaced with an [1 x i32] global and the icmp gets folded away. But at that point we no longer fold the zext.
24 lines
819 B
C
24 lines
819 B
C
// RUN: %clang_cc1 -emit-llvm-bc -disable-llvm-passes -o %t.bc %s
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// RUN: llvm-dis %t.bc -o - | FileCheck %s
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// Test case for PR45426. Make sure we do not crash while writing bitcode
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// containing a simplify-able fneg constant expression.
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//
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// CHECK-LABEL define i32 @main()
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// CHECK: entry:
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// CHECK-NEXT: %retval = alloca i32
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// CHECK-NEXT: store i32 0, ptr %retval
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// CHECK-NEXT: [[ZEXT:%.*]] = zext i1 true to i32
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// CHECK-NEXT: [[SITOFP:%.*]] = sitofp i32 [[ZEXT]] to float
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// CHECK-NEXT: [[LV:%.*]] = load ptr, ptr @c
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// CHECK-NEXT: store float [[SITOFP]], ptr [[LV]], align 4
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// CHECK-NEXT: [[FNEG:%.*]] = fneg float [[SITOFP]]
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// CHECK-NEXT: [[CONV:%.*]] = fptosi float [[FNEG]] to i32
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// CHECK-NEXT: ret i32 [[CONV]]
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int a[], b;
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float *c;
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int main(void) {
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return -(*c = &b != a);
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}
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