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llvm-mirror/test/Transforms/InstCombine/sub-ashr-or-to-icmp-select.ll
Nikita Popov 730509657a [InstCombine] DCE instructions earlier
When InstCombine initially populates the worklist, it already
performs constant folding and DCE. However, as the instructions
are initially visited in program order, this DCE can pick up only
the last instruction of a dead chain, the rest would only get
picked up in the main InstCombine run.

To avoid this, we instead perform the DCE in separate pass over the
collected instructions in reverse order, which will allow us to
pick up full dead instruction chains. We already need to do this
reverse iteration anyway to populate the worklist, so this
shouldn't add extra cost.

This by itself only fixes a small part of the problem though:
The same basic issue also applies during the main InstCombine loop.
We generally always want DCE to occur as early as possible,
because it will allow one-use folds to happen. Address this by also
performing DCE while adding deferred instructions to the main worklist.

This drops the number of tests that perform more than 2 InstCombine
iterations from ~80 to ~40. There's some spurious test changes due
to operand order / icmp toggling.

Differential Revision: https://reviews.llvm.org/D75008
2020-02-27 18:45:59 +01:00

240 lines
7.7 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -instcombine %s -S -o - | FileCheck %s
; Clamp positive to allOnes:
; E.g., clamp255 implemented in a shifty way, could be optimized as v > 255 ? 255 : v, where sub hasNoSignedWrap.
; int32 clamp255(int32 v) {
; return (((255 - (v)) >> 31) | (v)) & 255;
; }
;
; Scalar Types
define i32 @clamp255_i32(i32 %x) {
; CHECK-LABEL: @clamp255_i32(
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 255
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i32 [[X]], i32 255
; CHECK-NEXT: [[AND:%.*]] = and i32 [[OR]], 255
; CHECK-NEXT: ret i32 [[AND]]
;
%sub = sub nsw i32 255, %x
%shr = ashr i32 %sub, 31
%or = or i32 %shr, %x
%and = and i32 %or, 255
ret i32 %and
}
define i8 @sub_ashr_or_i8(i8 %x, i8 %y) {
; CHECK-LABEL: @sub_ashr_or_i8(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i8 -1, i8 [[X]]
; CHECK-NEXT: ret i8 [[OR]]
;
%sub = sub nsw i8 %y, %x
%shr = ashr i8 %sub, 7
%or = or i8 %shr, %x
ret i8 %or
}
define i16 @sub_ashr_or_i16(i16 %x, i16 %y) {
; CHECK-LABEL: @sub_ashr_or_i16(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i16 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i16 -1, i16 [[X]]
; CHECK-NEXT: ret i16 [[OR]]
;
%sub = sub nsw i16 %y, %x
%shr = ashr i16 %sub, 15
%or = or i16 %shr, %x
ret i16 %or
}
define i32 @sub_ashr_or_i32(i32 %x, i32 %y) {
; CHECK-LABEL: @sub_ashr_or_i32(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[X]]
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub nsw i32 %y, %x
%shr = ashr i32 %sub, 31
%or = or i32 %shr, %x
ret i32 %or
}
define i64 @sub_ashr_or_i64(i64 %x, i64 %y) {
; CHECK-LABEL: @sub_ashr_or_i64(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i64 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i64 -1, i64 [[X]]
; CHECK-NEXT: ret i64 [[OR]]
;
%sub = sub nsw i64 %y, %x
%shr = ashr i64 %sub, 63
%or = or i64 %shr, %x
ret i64 %or
}
; nuw nsw
define i32 @sub_ashr_or_i32_nuw_nsw(i32 %x, i32 %y) {
; CHECK-LABEL: @sub_ashr_or_i32_nuw_nsw(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[X]]
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub nuw nsw i32 %y, %x
%shr = ashr i32 %sub, 31
%or = or i32 %shr, %x
ret i32 %or
}
; Commute
define i32 @sub_ashr_or_i32_commute(i32 %x, i32 %y) {
; CHECK-LABEL: @sub_ashr_or_i32_commute(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[X]]
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub nsw i32 %y, %x
%shr = ashr i32 %sub, 31
%or = or i32 %x, %shr ; commute %shr and %x
ret i32 %or
}
; Vector Types
define <4 x i32> @sub_ashr_or_i32_vec(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @sub_ashr_or_i32_vec(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <4 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> <i32 -1, i32 -1, i32 -1, i32 -1>, <4 x i32> [[X]]
; CHECK-NEXT: ret <4 x i32> [[OR]]
;
%sub = sub nsw <4 x i32> %y, %x
%shr = ashr <4 x i32> %sub, <i32 31, i32 31, i32 31, i32 31>
%or = or <4 x i32> %shr, %x
ret <4 x i32> %or
}
define <4 x i32> @sub_ashr_or_i32_vec_nuw_nsw(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @sub_ashr_or_i32_vec_nuw_nsw(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <4 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> <i32 -1, i32 -1, i32 -1, i32 -1>, <4 x i32> [[X]]
; CHECK-NEXT: ret <4 x i32> [[OR]]
;
%sub = sub nuw nsw <4 x i32> %y, %x
%shr = ashr <4 x i32> %sub, <i32 31, i32 31, i32 31, i32 31>
%or = or <4 x i32> %shr, %x
ret <4 x i32> %or
}
define <4 x i32> @sub_ashr_or_i32_vec_commute(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @sub_ashr_or_i32_vec_commute(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <4 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> <i32 -1, i32 -1, i32 -1, i32 -1>, <4 x i32> [[X]]
; CHECK-NEXT: ret <4 x i32> [[OR]]
;
%sub = sub nsw <4 x i32> %y, %x
%shr = ashr <4 x i32> %sub, <i32 31, i32 31, i32 31, i32 31>
%or = or <4 x i32> %x, %shr
ret <4 x i32> %or
}
; Extra uses
define i32 @sub_ashr_or_i32_extra_use_sub(i32 %x, i32 %y, i32* %p) {
; CHECK-LABEL: @sub_ashr_or_i32_extra_use_sub(
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: store i32 [[SUB]], i32* [[P:%.*]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i32 [[Y]], [[X]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[X]]
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub nsw i32 %y, %x
store i32 %sub, i32* %p
%shr = ashr i32 %sub, 31
%or = or i32 %shr, %x
ret i32 %or
}
define i32 @sub_ashr_or_i32_extra_use_or(i32 %x, i32 %y, i32* %p) {
; CHECK-LABEL: @sub_ashr_or_i32_extra_use_or(
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[OR:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[X]]
; CHECK-NEXT: store i32 [[OR]], i32* [[P:%.*]], align 4
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub nsw i32 %y, %x
%shr = ashr i32 %sub, 31
%or = or i32 %shr, %x
store i32 %or, i32* %p
ret i32 %or
}
; Negative Tests
define i32 @sub_ashr_or_i32_extra_use_ashr(i32 %x, i32 %y, i32* %p) {
; CHECK-LABEL: @sub_ashr_or_i32_extra_use_ashr(
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[SHR:%.*]] = ashr i32 [[SUB]], 31
; CHECK-NEXT: store i32 [[SHR]], i32* [[P:%.*]], align 4
; CHECK-NEXT: [[OR:%.*]] = or i32 [[SHR]], [[X]]
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub nsw i32 %y, %x
%shr = ashr i32 %sub, 31
store i32 %shr, i32* %p
%or = or i32 %shr, %x
ret i32 %or
}
define i32 @sub_ashr_or_i32_no_nsw_nuw(i32 %x, i32 %y) {
; CHECK-LABEL: @sub_ashr_or_i32_no_nsw_nuw(
; CHECK-NEXT: [[SUB:%.*]] = sub i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[SHR:%.*]] = ashr i32 [[SUB]], 31
; CHECK-NEXT: [[OR:%.*]] = or i32 [[SHR]], [[X]]
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub i32 %y, %x
%shr = ashr i32 %sub, 31
%or = or i32 %shr, %x
ret i32 %or
}
define <4 x i32> @sub_ashr_or_i32_vec_undef1(<4 x i32> %x) {
; CHECK-LABEL: @sub_ashr_or_i32_vec_undef1(
; CHECK-NEXT: [[SUB:%.*]] = sub <4 x i32> <i32 255, i32 255, i32 undef, i32 255>, [[X:%.*]]
; CHECK-NEXT: [[SHR:%.*]] = ashr <4 x i32> [[SUB]], <i32 31, i32 31, i32 31, i32 31>
; CHECK-NEXT: [[OR:%.*]] = or <4 x i32> [[SHR]], [[X]]
; CHECK-NEXT: ret <4 x i32> [[OR]]
;
%sub = sub <4 x i32> <i32 255, i32 255, i32 undef, i32 255>, %x
%shr = ashr <4 x i32> %sub, <i32 31, i32 31, i32 31, i32 31>
%or = or <4 x i32> %shr, %x
ret <4 x i32> %or
}
define <4 x i32> @sub_ashr_or_i32_vec_undef2(<4 x i32> %x) {
; CHECK-LABEL: @sub_ashr_or_i32_vec_undef2(
; CHECK-NEXT: [[SUB:%.*]] = sub nsw <4 x i32> <i32 255, i32 255, i32 255, i32 255>, [[X:%.*]]
; CHECK-NEXT: [[SHR:%.*]] = ashr <4 x i32> [[SUB]], <i32 undef, i32 31, i32 31, i32 31>
; CHECK-NEXT: [[OR:%.*]] = or <4 x i32> [[SHR]], [[X]]
; CHECK-NEXT: ret <4 x i32> [[OR]]
;
%sub = sub nsw <4 x i32> <i32 255, i32 255, i32 255, i32 255>, %x
%shr = ashr <4 x i32> %sub, <i32 undef, i32 31, i32 31, i32 31>
%or = or <4 x i32> %shr, %x
ret <4 x i32> %or
}
define i32 @sub_ashr_or_i32_shift_wrong_bit(i32 %x, i32 %y) {
; CHECK-LABEL: @sub_ashr_or_i32_shift_wrong_bit(
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[SHR:%.*]] = ashr i32 [[SUB]], 11
; CHECK-NEXT: [[OR:%.*]] = or i32 [[SHR]], [[X]]
; CHECK-NEXT: ret i32 [[OR]]
;
%sub = sub nsw i32 %y, %x
%shr = ashr i32 %sub, 11
%or = or i32 %shr, %x
ret i32 %or
}