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[InstCombine] add/move tests for fsub folds; NFC

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There are a pair of folds that try to merge fneg into fsub
with an intervening cast, but as shown in the FIXME tests,
they can create extra instructions.

llvm-svn: 329501
This commit is contained in:
Sanjay Patel 2018-04-07 14:07:58 +00:00
parent 7a86538035
commit 5d9b2cef51
2 changed files with 100 additions and 24 deletions
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23
test/Transforms/InstCombine/fneg-ext.ll
View File

@ -1,23 +0,0 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; CHECK: test1
define double @test1(float %a, double %b) nounwind readnone ssp uwtable {
; CHECK-NOT: fsub
; CHECK: fpext
; CHECK: fadd
%1 = fsub float -0.000000e+00, %a
%2 = fpext float %1 to double
%3 = fsub double %b, %2
ret double %3
}
; CHECK: test2
define double @test2(float %a, double %b) nounwind readnone ssp uwtable {
; CHECK-NOT: fsub
; CHECK: fpext
; CHECK: fadd fast
%1 = fsub float -0.000000e+00, %a
%2 = fpext float %1 to double
%3 = fsub fast double %b, %2
ret double %3
}

101
test/Transforms/InstCombine/fsub.ll
View File

@ -28,10 +28,11 @@ define float @neg_sub_nsz(float %x, float %y) {
}
; If the subtract has another use, we don't do the transform (even though it
; doesn't increase the IR instruction count) because we assume that fneg is
; doesn't increase the IR instruction count) because we assume that fneg is
; easier to analyze and generally cheaper than generic fsub.
declare void @use(float)
declare void @use2(float, double)
define float @neg_sub_nsz_extra_use(float %x, float %y) {
; CHECK-LABEL: @neg_sub_nsz_extra_use(
@ -146,3 +147,101 @@ define <2 x float> @neg_op1_vec_undef(<2 x float> %x, <2 x float> %y) {
ret <2 x float> %r
}
; Similar to above - but look through fpext/fptrunc casts to find the fneg.
define double @neg_ext_op1(float %a, double %b) {
; CHECK-LABEL: @neg_ext_op1(
; CHECK-NEXT: [[TMP1:%.*]] = fpext float [[A:%.*]] to double
; CHECK-NEXT: [[T3:%.*]] = fadd double [[TMP1]], [[B:%.*]]
; CHECK-NEXT: ret double [[T3]]
;
%t1 = fsub float -0.0, %a
%t2 = fpext float %t1 to double
%t3 = fsub double %b, %t2
ret double %t3
}
; Verify that vectors work too.
define <2 x float> @neg_trunc_op1(<2 x double> %a, <2 x float> %b) {
; CHECK-LABEL: @neg_trunc_op1(
; CHECK-NEXT: [[TMP1:%.*]] = fptrunc <2 x double> [[A:%.*]] to <2 x float>
; CHECK-NEXT: [[T3:%.*]] = fadd <2 x float> [[TMP1]], [[B:%.*]]
; CHECK-NEXT: ret <2 x float> [[T3]]
;
%t1 = fsub <2 x double> <double -0.0, double -0.0>, %a
%t2 = fptrunc <2 x double> %t1 to <2 x float>
%t3 = fsub <2 x float> %b, %t2
ret <2 x float> %t3
}
; No FMF needed, but they should propagate to the fadd.
define double @neg_ext_op1_fast(float %a, double %b) {
; CHECK-LABEL: @neg_ext_op1_fast(
; CHECK-NEXT: [[TMP1:%.*]] = fpext float [[A:%.*]] to double
; CHECK-NEXT: [[T3:%.*]] = fadd fast double [[TMP1]], [[B:%.*]]
; CHECK-NEXT: ret double [[T3]]
;
%t1 = fsub float -0.0, %a
%t2 = fpext float %t1 to double
%t3 = fsub fast double %b, %t2
ret double %t3
}
; FIXME: Extra use should prevent the transform.
define float @neg_ext_op1_extra_use(half %a, float %b) {
; CHECK-LABEL: @neg_ext_op1_extra_use(
; CHECK-NEXT: [[T1:%.*]] = fsub half 0xH8000, [[A:%.*]]
; CHECK-NEXT: [[T2:%.*]] = fpext half [[T1]] to float
; CHECK-NEXT: [[TMP1:%.*]] = fpext half [[A]] to float
; CHECK-NEXT: [[T3:%.*]] = fadd float [[TMP1]], [[B:%.*]]
; CHECK-NEXT: call void @use(float [[T2]])
; CHECK-NEXT: ret float [[T3]]
;
%t1 = fsub half -0.0, %a
%t2 = fpext half %t1 to float
%t3 = fsub float %b, %t2
call void @use(float %t2)
ret float %t3
}
; One-use fptrunc is always hoisted above fneg, so the corresponding
; multi-use bug for fptrunc isn't visible with a fold starting from
; the last fsub.
define float @neg_trunc_op1_extra_use(double %a, float %b) {
; CHECK-LABEL: @neg_trunc_op1_extra_use(
; CHECK-NEXT: [[TMP1:%.*]] = fptrunc double [[A:%.*]] to float
; CHECK-NEXT: [[T2:%.*]] = fsub float -0.000000e+00, [[TMP1]]
; CHECK-NEXT: [[T3:%.*]] = fadd float [[TMP1]], [[B:%.*]]
; CHECK-NEXT: call void @use(float [[T2]])
; CHECK-NEXT: ret float [[T3]]
;
%t1 = fsub double -0.0, %a
%t2 = fptrunc double %t1 to float
%t3 = fsub float %b, %t2
call void @use(float %t2)
ret float %t3
}
; FIXME: But the bug is visible when both preceding values have other uses.
; Extra uses should prevent the transform.
define float @neg_trunc_op1_extra_uses(double %a, float %b) {
; CHECK-LABEL: @neg_trunc_op1_extra_uses(
; CHECK-NEXT: [[T1:%.*]] = fsub double -0.000000e+00, [[A:%.*]]
; CHECK-NEXT: [[T2:%.*]] = fptrunc double [[T1]] to float
; CHECK-NEXT: [[TMP1:%.*]] = fptrunc double [[A]] to float
; CHECK-NEXT: [[T3:%.*]] = fadd float [[TMP1]], [[B:%.*]]
; CHECK-NEXT: call void @use2(float [[T2]], double [[T1]])
; CHECK-NEXT: ret float [[T3]]
;
%t1 = fsub double -0.0, %a
%t2 = fptrunc double %t1 to float
%t3 = fsub float %b, %t2
call void @use2(float %t2, double %t1)
ret float %t3
}