RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-23 03:02:36 +01:00
Code Issues Projects Releases Wiki Activity

[instcombine] Collapse trivial or recurrences

Browse Source 
If we have a recurrence of the form <Start, Or, Step> we know that the value taken by the recurrence stabilizes on the first iteration (provided step is loop invariant). We can exploit that fact to remove the loop carried dependence in the recurrence.

Differential Revision: https://reviews.llvm.org/D97578 (or part)
This commit is contained in:
Philip Reames 2021-03-08 09:17:11 -08:00
parent cb80fb2e0c
commit 004f73aeb1
2 changed files with 12 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -2843,6 +2843,12 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
if (sinkNotIntoOtherHandOfAndOrOr(I))
return &I;
// An or recurrence w/loop invariant step is equivelent to (or start, step)
PHINode *PN = nullptr;
Value *Start = nullptr, *Step = nullptr;
if (matchSimpleRecurrence(&I, PN, Start, Step) && DT.dominates(Step, PN))
return replaceInstUsesWith(I, Builder.CreateOr(Start, Step));
return nullptr;
}

15
test/Transforms/InstCombine/recurrence.ll
View File

@ -6,9 +6,8 @@ define i64 @test_or(i64 %a) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[A:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[IV_NEXT]] = or i64 [[IV]], 15
; CHECK-NEXT: tail call void @use(i64 [[IV_NEXT]])
; CHECK-NEXT: [[TMP0:%.*]] = or i64 [[A:%.*]], 15
; CHECK-NEXT: tail call void @use(i64 [[TMP0]])
; CHECK-NEXT: br label [[LOOP]]
;
entry:
@ -27,9 +26,8 @@ define i64 @test_or2(i64 %a, i64 %b) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[A:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[IV_NEXT]] = or i64 [[IV]], [[B:%.*]]
; CHECK-NEXT: tail call void @use(i64 [[IV_NEXT]])
; CHECK-NEXT: [[TMP0:%.*]] = or i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: tail call void @use(i64 [[TMP0]])
; CHECK-NEXT: br label [[LOOP]]
;
entry:
@ -47,9 +45,8 @@ define i64 @test_or3(i64 %a, i64 %b) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[A:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[IV_NEXT]] = or i64 [[IV]], [[B:%.*]]
; CHECK-NEXT: tail call void @use(i64 [[IV_NEXT]])
; CHECK-NEXT: [[TMP0:%.*]] = or i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: tail call void @use(i64 [[TMP0]])
; CHECK-NEXT: br label [[LOOP]]
;
entry: