From ec905a62ae26fd3b2064a15e31b9988a8d32589a Mon Sep 17 00:00:00 2001
From: James Molloy <james.molloy@arm.com>
Date: Wed, 7 Sep 2016 08:40:20 +0000
Subject: [PATCH] [SimplifyCFG] Update workaround for PR30188 to also include
 loads

I should have realised this the first time around, but if we're avoiding sinking stores where the operands come from allocas so they don't create selects, we also have to do the same for loads because SROA will be just as defective looking at loads of selected addresses as stores.

Fixes PR30188 (again).

llvm-svn: 280792
---
 llvm/lib/Transforms/Utils/SimplifyCFG.cpp          |  9 +++++--
 .../Transforms/SimplifyCFG/sink-common-code.ll     | 29 ++++++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 6252169..909a72c2 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1428,8 +1428,8 @@ static bool canSinkInstructions(
         return false;
       }
       // Because SROA can't handle speculating stores of selects, try not
-      // to sink stores of allocas when we'd have to create a PHI for the
-      // address operand.
+      // to sink loads or stores of allocas when we'd have to create a PHI for
+      // the address operand.
       // FIXME: This is a workaround for a deficiency in SROA - see
       // https://llvm.org/bugs/show_bug.cgi?id=30188
       if (OI == 1 && isa<StoreInst>(I0) &&
@@ -1437,6 +1437,11 @@ static bool canSinkInstructions(
             return isa<AllocaInst>(I->getOperand(1));
           }))
         return false;
+      if (OI == 0 && isa<LoadInst>(I0) &&
+          any_of(Insts, [](const Instruction *I) {
+            return isa<AllocaInst>(I->getOperand(0));
+          }))
+        return false;
       for (auto *I : Insts)
         PHIOperands[I].push_back(I->getOperand(OI));
     }
diff --git a/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll b/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
index 57533fa..b20b53c 100644
--- a/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
+++ b/llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
@@ -585,6 +585,35 @@ if.end:
 ; CHECK: store
 ; CHECK: store
 
+define i32 @test_pr30188a(i1 zeroext %flag, i32 %x) {
+entry:
+  %y = alloca i32
+  %z = alloca i32
+  br i1 %flag, label %if.then, label %if.else
+
+if.then:
+  call void @g()
+  %one = load i32, i32* %y
+  %two = add i32 %one, 2
+  store i32 %two, i32* %y
+  br label %if.end
+
+if.else:
+  %three = load i32, i32* %z
+  %four = add i32 %three, 2
+  store i32 %four, i32* %y
+  br label %if.end
+
+if.end:
+  ret i32 1
+}
+
+; CHECK-LABEL: test_pr30188a
+; CHECK-NOT: select
+; CHECK: load
+; CHECK: load
+; CHECK: store
+
 ; The phi is confusing - both add instructions are used by it, but
 ; not on their respective unconditional arcs. It should not be
 ; optimized.
-- 
2.7.4