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61f35cd2aa
It was recently discovered that the handling of CC values was actually broken
since overflow was not properly handled ('nsw' flag not checked for).
Add and sub instructions now have a new target specific instruction flag
named SystemZII::CCIfNoSignedWrap. It means that the CC result can be used
instead of a compare with 0, but only if the instruction has the 'nsw' flag
set.
This patch also adds the improvements of conversion to logical instructions
and the analyzing of add with immediates, to be able to eliminate more
compares.
Review: Ulrich Weigand
https://reviews.llvm.org/D66868
104 lines
2.4 KiB
LLVM
104 lines
2.4 KiB
LLVM
; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14 -disable-cgp | FileCheck %s
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;
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; Check that signed comparisons against 0 are eliminated if the defining
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; instruction is an add with immediate.
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;
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; Addition of an immediate does not depend on the "nsw" flag, since the
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; result can be predicted in case of overflow. For example, if adding a
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; positive immediate gives overflow, the result must be negative.
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; Addition of a negative immediate gives a positive result in case of
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; overflow (except for the case of the minimum value which may also result in
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; a zero result).
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define i32 @fun0(i32 %arg) {
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; CHECK-LABEL: fun0:
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; CHECK: ahik
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; CHECK-NEXT: locre
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bb:
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%tmp = add i32 %arg, -1
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%tmp1 = icmp eq i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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define i32 @fun1(i32 %arg) {
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; CHECK-LABEL: fun1:
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; CHECK: ahik
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; CHECK-NEXT: locrnle
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bb:
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%tmp = add i32 %arg, -1
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%tmp1 = icmp sgt i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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define i32 @fun2(i32 %arg) {
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; CHECK-LABEL: fun2:
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; CHECK: ahik
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; CHECK-NEXT: locrl
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bb:
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%tmp = add i32 %arg, -1
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%tmp1 = icmp slt i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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; Addition of a positive immediate gives a negative result in case of overflow.
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define i32 @fun3(i32 %arg) {
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; CHECK-LABEL: fun3:
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; CHECK: ahik
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; CHECK-NEXT: locre
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bb:
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%tmp = add i32 %arg, 1
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%tmp1 = icmp eq i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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define i32 @fun4(i32 %arg) {
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; CHECK-LABEL: fun4:
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; CHECK: ahik
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; CHECK-NEXT: locrh
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bb:
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%tmp = add i32 %arg, 1
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%tmp1 = icmp sgt i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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define i32 @fun5(i32 %arg) {
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; CHECK-LABEL: fun5:
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; CHECK: ahik
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; CHECK-NEXT: locrnhe
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bb:
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%tmp = add i32 %arg, 1
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%tmp1 = icmp slt i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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; Addition of the minimum value gives a positive or zero result.
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define i32 @fun6(i32 %arg) {
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; CHECK-LABEL: fun6:
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; CHECK: afi
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; CHECK-NEXT: chi
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; CHECK-NEXT: locrlh
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bb:
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%tmp = add i32 %arg, -2147483648
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%tmp1 = icmp eq i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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define i32 @fun7(i32 %arg) {
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; CHECK-LABEL: fun7:
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; CHECK: afi
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; CHECK-NEXT: chi
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; CHECK-NEXT: locrle
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bb:
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%tmp = add i32 %arg, -2147483648
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%tmp1 = icmp sgt i32 %tmp, 0
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%res = select i1 %tmp1, i32 %tmp, i32 %arg
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ret i32 %res
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}
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