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6c28a7eec8
test case on PowerPC caused by rounding errors when converting from a 64-bit integer to a single-precision floating point. The reason for this are double-rounding effects, since on PowerPC we have to convert to an intermediate double-precision value first, which gets rounded to the final single-precision result. The patch fixes the problem by preparing the 64-bit integer so that the first conversion step to double-precision will always be exact, and the final rounding step will result in the correctly-rounded single-precision result. The generated code sequence is equivalent to what GCC would generate. When -enable-unsafe-fp-math is in effect, that extra effort is omitted and we accept possible rounding errors (just like GCC does as well). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166178 91177308-0d34-0410-b5e6-96231b3b80d8
28 lines
973 B
LLVM
28 lines
973 B
LLVM
; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
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target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32:64"
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target triple = "powerpc64-unknown-linux-gnu"
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define float @test(i64 %x) nounwind readnone {
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entry:
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%conv = sitofp i64 %x to float
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ret float %conv
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}
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; Verify that we get the code sequence needed to avoid double-rounding.
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; Note that only parts of the sequence are checked for here, to allow
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; for minor code generation differences.
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; CHECK: sradi [[REGISTER:[0-9]+]], 3, 53
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; CHECK: addi [[REGISTER:[0-9]+]], [[REGISTER]], 1
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; CHECK: cmpldi 0, [[REGISTER]], 1
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; CHECK: isel [[REGISTER:[0-9]+]], {{[0-9]+}}, 3, 1
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; CHECK: std [[REGISTER]], -{{[0-9]+}}(1)
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; Also check that with -enable-unsafe-fp-math we do not get that extra
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; code sequence. Simply verify that there is no "isel" present.
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; RUN: llc -mcpu=pwr7 -enable-unsafe-fp-math < %s | FileCheck %s -check-prefix=UNSAFE
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; CHECK-UNSAFE-NOT: isel
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