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llvm-project/llvm/test/CodeGen/X86/fp-double-rounding.ll

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[CodeGen] Don't blindly combine (fp_round (fp_round x)) to (fp_round x). 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 llvm-svn: 228911
2015-02-12 14:15:29 +08:00
; RUN: llc < %s | FileCheck %s --check-prefix=CHECK --check-prefix=SAFE
; RUN: llc < %s -enable-unsafe-fp-math | FileCheck %s --check-prefix=CHECK --check-prefix=UNSAFE
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64--"
; CHECK-LABEL: double_rounding:
; SAFE: callq __trunctfdf2
; SAFE-NEXT: cvtsd2ss %xmm0
; UNSAFE: callq __trunctfsf2
; UNSAFE-NOT: cvt
define void @double_rounding(fp128* %x, float* %f) {
entry:
[opaque pointer type] Add textual IR support for explicit type parameter to load instruction Essentially the same as the GEP change in r230786. A similar migration script can be used to update test cases, though a few more test case improvements/changes were required this time around: (r229269-r229278) import fileinput import sys import re pat = re.compile(r"((?:=|:|^)\s*load (?:atomic )?(?:volatile )?(.*?))(| addrspace\(\d+\) *)\*($| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$)") for line in sys.stdin: sys.stdout.write(re.sub(pat, r"\1, \2\3*\4", line)) Reviewers: rafael, dexonsmith, grosser Differential Revision: http://reviews.llvm.org/D7649 llvm-svn: 230794
2015-02-28 05:17:42 +08:00
%0 = load fp128, fp128* %x, align 16
[CodeGen] Don't blindly combine (fp_round (fp_round x)) to (fp_round x). 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 llvm-svn: 228911
2015-02-12 14:15:29 +08:00
%1 = fptrunc fp128 %0 to double
%2 = fptrunc double %1 to float
store float %2, float* %f, align 4
ret void
}
; CHECK-LABEL: double_rounding_precise_first:
; CHECK: fstps (%
; CHECK-NOT: fstpl
define void @double_rounding_precise_first(float* %f) {
entry:
; Hack, to generate a precise FP_ROUND to double
%precise = call double asm sideeffect "fld %st(0)", "={st(0)}"()
%0 = fptrunc double %precise to float
store float %0, float* %f, align 4
ret void
}