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9e9bde9b54
We used to do this DAG combine, but it's not always correct: If the first fp_round isn't a value preserving truncation, it might introduce a tie in the second fp_round, that wouldn't occur in the single-step fp_round we want to fold to. In other words, double rounding isn't the same as rounding. Differential Revision: http://reviews.llvm.org/D7571 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228911 91177308-0d34-0410-b5e6-96231b3b80d8
32 lines
957 B
LLVM
32 lines
957 B
LLVM
; RUN: llc < %s | FileCheck %s --check-prefix=CHECK --check-prefix=SAFE
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; RUN: llc < %s -enable-unsafe-fp-math | FileCheck %s --check-prefix=CHECK --check-prefix=UNSAFE
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64--"
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; CHECK-LABEL: double_rounding:
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; SAFE: callq __trunctfdf2
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; SAFE-NEXT: cvtsd2ss %xmm0
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; UNSAFE: callq __trunctfsf2
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; UNSAFE-NOT: cvt
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define void @double_rounding(fp128* %x, float* %f) {
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entry:
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%0 = load fp128* %x, align 16
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%1 = fptrunc fp128 %0 to double
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%2 = fptrunc double %1 to float
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store float %2, float* %f, align 4
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ret void
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}
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; CHECK-LABEL: double_rounding_precise_first:
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; CHECK: fstps (%
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; CHECK-NOT: fstpl
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define void @double_rounding_precise_first(float* %f) {
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entry:
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; Hack, to generate a precise FP_ROUND to double
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%precise = call double asm sideeffect "fld %st(0)", "={st(0)}"()
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%0 = fptrunc double %precise to float
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store float %0, float* %f, align 4
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ret void
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}
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