mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-07-25 13:24:46 +00:00
This patch fixes failures in the SingleSource/Regression/C/uint64_to_float
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
This commit is contained in:
27
test/CodeGen/PowerPC/i64_fp_round.ll
Normal file
27
test/CodeGen/PowerPC/i64_fp_round.ll
Normal file
@@ -0,0 +1,27 @@
|
||||
; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
|
||||
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"
|
||||
target triple = "powerpc64-unknown-linux-gnu"
|
||||
|
||||
define float @test(i64 %x) nounwind readnone {
|
||||
entry:
|
||||
%conv = sitofp i64 %x to float
|
||||
ret float %conv
|
||||
}
|
||||
|
||||
; Verify that we get the code sequence needed to avoid double-rounding.
|
||||
; Note that only parts of the sequence are checked for here, to allow
|
||||
; for minor code generation differences.
|
||||
|
||||
; CHECK: sradi [[REGISTER:[0-9]+]], 3, 53
|
||||
; CHECK: addi [[REGISTER:[0-9]+]], [[REGISTER]], 1
|
||||
; CHECK: cmpldi 0, [[REGISTER]], 1
|
||||
; CHECK: isel [[REGISTER:[0-9]+]], {{[0-9]+}}, 3, 1
|
||||
; CHECK: std [[REGISTER]], -{{[0-9]+}}(1)
|
||||
|
||||
|
||||
; Also check that with -enable-unsafe-fp-math we do not get that extra
|
||||
; code sequence. Simply verify that there is no "isel" present.
|
||||
|
||||
; RUN: llc -mcpu=pwr7 -enable-unsafe-fp-math < %s | FileCheck %s -check-prefix=UNSAFE
|
||||
; CHECK-UNSAFE-NOT: isel
|
||||
|
Reference in New Issue
Block a user