[PATCH] D19095: [BPI] Consider deoptimize calls as "unreachable"

[Sanjoy Das via llvm-commits]

sanjoy created this revision.
sanjoy added a reviewer: chandlerc.
sanjoy added a subscriber: llvm-commits.
Herald added a subscriber: mcrosier.

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

http://reviews.llvm.org/D19095

Files:
  lib/Analysis/BranchProbabilityInfo.cpp
  test/Analysis/BranchProbabilityInfo/deopt-intrinsic.ll

Index: test/Analysis/BranchProbabilityInfo/deopt-intrinsic.ll
===================================================================
--- /dev/null
+++ test/Analysis/BranchProbabilityInfo/deopt-intrinsic.ll
@@ -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
+}
Index: lib/Analysis/BranchProbabilityInfo.cpp
===================================================================
--- lib/Analysis/BranchProbabilityInfo.cpp
+++ lib/Analysis/BranchProbabilityInfo.cpp
@@ -115,7 +115,12 @@
 bool BranchProbabilityInfo::calcUnreachableHeuristics(BasicBlock *BB) {
   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;
   }


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