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Testcase for r109556. Radar 8198362.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109557 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Stuart Hastings 2010-07-27 23:15:25 +00:00
parent b344a346f1
commit 3c73a6b650
1 changed files with 18 additions and 0 deletions
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test/FrontendC/2010-07-27-MinNoFoldConst.c Normal file
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// RUN: %llvmgcc -S %s -o - | FileCheck %s
extern int printf(const char *, ...);
static void bad(unsigned int v1, unsigned int v2) {
printf("%u\n", 1631381461u * (((v2 - 1273463329u <= v1 - 1273463329u) ? v2 : v1) - 1273463329u) + 121322179u);
}
// Radar 8198362
// GCC FE wants to convert the above to
// 1631381461u * MIN(v2 - 1273463329u, v1 - 1273463329u)
// and then to
// MIN(1631381461u * v2 - 4047041419, 1631381461u * v1 - 4047041419)
//
// 1631381461u * 1273463329u = 2077504466193943669, but 32-bit overflow clips
// this to 4047041419. This breaks the comparision implicit in the MIN().
// Two multiply operations suggests the bad optimization is happening;
// one multiplication, after the MIN(), is correct.
// CHECK: mul
// CHECK-NOT: mul
// CHECK: ret