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[BPI] Consider deoptimize calls as "unreachable"

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Summary:
Calls to @llvm.experimental.deoptimize are expected to "never execute",
so optimize them as such.

Reviewers: chandlerc

Subscribers: junbuml, mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D19095

llvm-svn: 266654
This commit is contained in:
Sanjoy Das 2016-04-18 19:01:28 +00:00
parent e9233149ee
commit f97ce19844
2 changed files with 26 additions and 1 deletions
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7
lib/Analysis/BranchProbabilityInfo.cpp
View File

@ -115,7 +115,12 @@ static const uint32_t IH_NONTAKEN_WEIGHT = 1;
bool BranchProbabilityInfo::calcUnreachableHeuristics(const BasicBlock *BB) {
const TerminatorInst *TI = BB->getTerminator();
if (TI->getNumSuccessors() == 0) {
if (isa<UnreachableInst>(TI))
if (isa<UnreachableInst>(TI) ||
// If this block is terminated by a call to
// @llvm.experimental.deoptimize then treat it like an unreachable since
// the @llvm.experimental.deoptimize call is expected to practically
// never execute.
BB->getTerminatingDeoptimizeCall())
PostDominatedByUnreachable.insert(BB);
return false;
}

20
test/Analysis/BranchProbabilityInfo/deopt-intrinsic.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: opt -analyze -branch-prob < %s | FileCheck %s
declare i32 @llvm.experimental.deoptimize.i32(...)
define i32 @test1(i32 %a, i32 %b) {
; CHECK-LABEL: Printing analysis 'Branch Probability Analysis' for function 'test1':
entry:
%cond = icmp eq i32 %a, 42
br i1 %cond, label %exit, label %deopt
; CHECK: edge entry -> exit probability is 0x7ffff800 / 0x80000000 = 100.00% [HOT edge]
; CHECK: edge entry -> deopt probability is 0x00000800 / 0x80000000 = 0.00%
deopt:
%rval = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"() ]
ret i32 %rval
exit:
ret i32 %b
}