[PATCH] D37821: [SimplifyCfg] Don't sink loads/stores to geps of allocas

[Ariel Ben-Yehuda via Phabricator via llvm-commits]

arielb1 created this revision.

This makes to workaround to PR30188 be more robust to code that uses structs.

In practice, this improves an optimization case in rustc and reduces in-the-wild Rust code size by 0.1%.


https://reviews.llvm.org/D37821

Files:
  lib/Transforms/Utils/SimplifyCFG.cpp
  test/Transforms/SimplifyCFG/sink-common-code.ll


Index: test/Transforms/SimplifyCFG/sink-common-code.ll
===================================================================
--- test/Transforms/SimplifyCFG/sink-common-code.ll
+++ test/Transforms/SimplifyCFG/sink-common-code.ll
@@ -657,6 +657,31 @@
 ; CHECK: load
 ; CHECK: store
 
+define i32 @test_pr30188b(i1 zeroext %flag, i32 %x) {
+entry:
+  %yy = alloca {i32}
+  %zz = alloca {i32}
+  %y = getelementptr inbounds {i32}, {i32}* %y, i32 0, i32 ,0
+  %z = getelementptr inbounds {i32}, {i32}* %z, i32 0, i32 ,0
+  br i1 %flag, label %if.then, label %if.else
+
+if.then:
+  store i32 %x, i32* %y
+  br label %if.end
+
+if.else:
+  store i32 %x, i32* %z
+  br label %if.end
+
+if.end:
+  ret i32 1
+}
+
+; CHECK-LABEL: test_pr30188b
+; CHECK-NOT: select
+; CHECK: store
+; 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.
Index: lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyCFG.cpp
+++ lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1436,11 +1436,11 @@
   // FIXME: This is a workaround for a deficiency in SROA - see
   // https://llvm.org/bugs/show_bug.cgi?id=30188
   if (isa<StoreInst>(I0) && any_of(Insts, [](const Instruction *I) {
-        return isa<AllocaInst>(I->getOperand(1));
+        return isa<AllocaInst>(I->getOperand(1)->stripInBoundsOffsets());
       }))
     return false;
   if (isa<LoadInst>(I0) && any_of(Insts, [](const Instruction *I) {
-        return isa<AllocaInst>(I->getOperand(0));
+        return isa<AllocaInst>(I->getOperand(0)->stripInBoundsOffsets());
       }))
     return false;
 


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