2016-08-19 16:38:50 +08:00
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; RUN: llc < %s | FileCheck %s
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target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
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target triple = "aarch64"
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[Legalizer] Fix fp-to-uint to fp-tosint promotion assertion.
Summary:
When promoting fp-to-uint16 to fp-to-sint32, the result is actually zero
extended. For example, given double 65534.0, without legalization:
fp-to-uint16: 65534.0 -> 0xfffe
With the legalization:
fp-to-sint32: 65534.0 -> 0x0000fffe
Without this patch, legalization wrongly emits a signed extend assertion,
which is consumed by later icmp instruction, and cause miscompile.
Note that the floating point value must be in [0, 65535), otherwise the
behavior is undefined.
This patch reverts r279223 behavior and adds more tests and
documentations.
In PR29041's context, James Molloy mentioned that:
We don't need to mask because conversion from float->uint8_t is
undefined if the integer part of the float value is not representable in
uint8_t. Therefore we can assume this doesn't happen!
which is totally true and good, because fptoui is documented clearly to
have undefined behavior when overflow/underflow happens. We should take
the advantage of this behavior so that we can save unnecessary mask
instructions.
Reviewers: jmolloy, nadav, echristo, kbarton
Subscribers: mehdi_amini, nemanjai, llvm-commits
Differential Revision: https://reviews.llvm.org/D28284
llvm-svn: 291015
2017-01-05 06:11:42 +08:00
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; If the float value is negative or too large, the result is undefined anyway;
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; otherwise, fcvtzs must returns a value in [0, 256), which guarantees zext.
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2016-08-19 16:38:50 +08:00
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; CHECK-LABEL: float_char_int_func:
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; CHECK: fcvtzs [[A:w[0-9]+]], s0
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; CHECK-NEXT: ret
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define i32 @float_char_int_func(float %infloatVal) {
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entry:
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%conv = fptoui float %infloatVal to i8
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%conv1 = zext i8 %conv to i32
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ret i32 %conv1
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}
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