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[SimplifyCFG] Fold branch to common dest: if branch is unpredictable, prefer to speculate 

This is consistent with the two other usages of prof md in this pass.
This commit is contained in:
Roman Lebedev 2021-07-26 02:57:19 +03:00
parent 59a5964e03
commit c2dacb1cd3
No known key found for this signature in database
GPG Key ID: 083C3EBB4A1689E0
2 changed files with 19 additions and 18 deletions
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3
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -3054,7 +3054,8 @@ shouldFoldCondBranchesToCommonDestination(BranchInst *BI, BranchInst *PBI,
// predecessor branch is predictable, we may not want to merge them.
uint64_t PTWeight, PFWeight;
BranchProbability PBITrueProb, Likely;
if (TTI && PBI->extractProfMetadata(PTWeight, PFWeight) &&
if (TTI && !PBI->getMetadata(LLVMContext::MD_unpredictable) &&
PBI->extractProfMetadata(PTWeight, PFWeight) &&
(PTWeight + PFWeight) != 0) {
PBITrueProb =
BranchProbability::getBranchProbability(PTWeight, PTWeight + PFWeight);

34
llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll
View File

@ -733,10 +733,9 @@ define void @or_icmps_probably_not_harmful(i32 %x, i32 %y, i8* %p) {
; CHECK-LABEL: @or_icmps_probably_not_harmful(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[EXPECTED_TRUE:%.*]] = icmp sgt i32 [[X:%.*]], -1
; CHECK-NEXT: br i1 [[EXPECTED_TRUE]], label [[EXIT:%.*]], label [[RARE:%.*]], !prof [[PROF19]], !unpredictable !21
; CHECK: rare:
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: br i1 [[EXPENSIVE]], label [[EXIT]], label [[FALSE:%.*]]
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_TRUE]], i1 true, i1 [[EXPENSIVE]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF21:![0-9]+]], !unpredictable !22
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -768,7 +767,7 @@ define void @or_icmps_not_that_harmful(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_TRUE:%.*]] = icmp sgt i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_TRUE]], i1 true, i1 [[EXPENSIVE]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF22:![0-9]+]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF23:![0-9]+]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -800,7 +799,7 @@ define void @or_icmps_not_that_harmful_inverted(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_TRUE:%.*]] = icmp sgt i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_TRUE]], i1 true, i1 [[EXPENSIVE]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF23:![0-9]+]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF24:![0-9]+]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -831,7 +830,7 @@ define void @or_icmps_useful(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_TRUE:%.*]] = icmp sle i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_TRUE]], i1 true, i1 [[EXPENSIVE]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF24:![0-9]+]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF25:![0-9]+]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -862,7 +861,7 @@ define void @or_icmps_useful_inverted(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_FALSE:%.*]] = icmp sgt i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_FALSE]], i1 true, i1 [[EXPENSIVE]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF24]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[EXIT:%.*]], label [[FALSE:%.*]], !prof [[PROF25]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -991,7 +990,7 @@ define void @and_icmps_not_that_harmful(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_FALSE:%.*]] = icmp sgt i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_FALSE]], i1 [[EXPENSIVE]], i1 false
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF25:![0-9]+]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF26:![0-9]+]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -1023,7 +1022,7 @@ define void @and_icmps_not_that_harmful_inverted(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_TRUE:%.*]] = icmp sle i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_TRUE]], i1 [[EXPENSIVE]], i1 false
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF25]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF26]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -1054,7 +1053,7 @@ define void @and_icmps_useful(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_TRUE:%.*]] = icmp sgt i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_TRUE]], i1 [[EXPENSIVE]], i1 false
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF26:![0-9]+]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF27:![0-9]+]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -1085,7 +1084,7 @@ define void @and_icmps_useful_inverted(i32 %x, i32 %y, i8* %p) {
; CHECK-NEXT: [[EXPECTED_FALSE:%.*]] = icmp sle i32 [[X:%.*]], -1
; CHECK-NEXT: [[EXPENSIVE:%.*]] = icmp eq i32 [[Y:%.*]], 0
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[EXPECTED_FALSE]], i1 [[EXPENSIVE]], i1 false
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF26]]
; CHECK-NEXT: br i1 [[OR_COND]], label [[FALSE:%.*]], label [[EXIT:%.*]], !prof [[PROF27]]
; CHECK: false:
; CHECK-NEXT: store i8 42, i8* [[P:%.*]], align 1
; CHECK-NEXT: br label [[EXIT]]
@ -1157,10 +1156,11 @@ exit:
; CHECK: [[PROF18]] = !{!"branch_weights", i32 8, i32 2}
; CHECK: [[PROF19]] = !{!"branch_weights", i32 99, i32 1}
; CHECK: [[PROF20]] = !{!"branch_weights", i32 1, i32 99}
; CHECK: [[META21:![0-9]+]] = !{}
; CHECK: [[PROF22]] = !{!"branch_weights", i32 197, i32 1}
; CHECK: [[PROF23]] = !{!"branch_weights", i32 100, i32 98}
; CHECK: [[PROF24]] = !{!"branch_weights", i32 101, i32 99}
; CHECK: [[PROF25]] = !{!"branch_weights", i32 1, i32 197}
; CHECK: [[PROF26]] = !{!"branch_weights", i32 99, i32 101}
; CHECK: [[PROF21]] = !{!"branch_weights", i32 199, i32 1}
; CHECK: [[META22:![0-9]+]] = !{}
; CHECK: [[PROF23]] = !{!"branch_weights", i32 197, i32 1}
; CHECK: [[PROF24]] = !{!"branch_weights", i32 100, i32 98}
; CHECK: [[PROF25]] = !{!"branch_weights", i32 101, i32 99}
; CHECK: [[PROF26]] = !{!"branch_weights", i32 1, i32 197}
; CHECK: [[PROF27]] = !{!"branch_weights", i32 99, i32 101}
;.