[llvm] r276181 - [GVNHoist] Don't hoist PHI nodes

[David Majnemer via llvm-commits]

Author: majnemer
Date: Wed Jul 20 16:05:01 2016
New Revision: 276181

URL: http://llvm.org/viewvc/llvm-project?rev=276181&view=rev
Log:
[GVNHoist] Don't hoist PHI nodes

We hoisted PHIs without respecting their special insertion point in the
block, leading to verfier errors.

This fixes PR28626.

Added:
    llvm/trunk/test/Transforms/GVN/pr28626.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp?rev=276181&r1=276180&r2=276181&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp Wed Jul 20 16:05:01 2016
@@ -576,16 +576,20 @@ public:
 
   bool makeOperandsAvailable(Instruction *Repl, BasicBlock *HoistPt) const {
     // Check whether the GEP of a ld/st can be synthesized at HoistPt.
-    Instruction *Gep = nullptr;
+    GetElementPtrInst *Gep = nullptr;
     Instruction *Val = nullptr;
     if (auto *Ld = dyn_cast<LoadInst>(Repl))
-      Gep = dyn_cast<Instruction>(Ld->getPointerOperand());
+      Gep = dyn_cast<GetElementPtrInst>(Ld->getPointerOperand());
     if (auto *St = dyn_cast<StoreInst>(Repl)) {
-      Gep = dyn_cast<Instruction>(St->getPointerOperand());
+      Gep = dyn_cast<GetElementPtrInst>(St->getPointerOperand());
       Val = dyn_cast<Instruction>(St->getValueOperand());
     }
 
-    if (!Gep || !isa<GetElementPtrInst>(Gep))
+    if (!Gep)
+      return false;
+
+    // PHIs may only be inserted at the start of a block.
+    if (Val && isa<PHINode>(Val))
       return false;
 
     // Check whether we can compute the Gep at HoistPt.

Added: llvm/trunk/test/Transforms/GVN/pr28626.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/pr28626.ll?rev=276181&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GVN/pr28626.ll (added)
+++ llvm/trunk/test/Transforms/GVN/pr28626.ll Wed Jul 20 16:05:01 2016
@@ -0,0 +1,42 @@
+; RUN: opt -S -gvn-hoist < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @test1(i1 %a, i1** %d) {
+entry:
+  %0 = load i1*, i1** %d, align 8
+  br i1 %a, label %if.then, label %if.else
+
+if.then:                                          ; preds = %entry
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %c.0 = phi i1 [ 1, %if.then ], [ 0, %if.else ]
+  br i1 %c.0, label %if.then2, label %if.else3
+
+if.then2:                                         ; preds = %if.end
+  %rc = getelementptr inbounds i1, i1* %0, i64 0
+  store i1 %c.0, i1* %rc, align 4
+  br label %if.end6
+
+if.else3:                                         ; preds = %if.end
+  %rc5 = getelementptr inbounds i1, i1* %0, i64 0
+  store i1 %c.0, i1* %rc5, align 4
+  br label %if.end6
+
+if.end6:                                          ; preds = %if.else3, %if.then2
+  ret void
+}
+
+; CHECK-LABEL: define void @test1(
+; CHECK:  %[[load:.*]] = load i1*, i1** %d, align 8
+; CHECK:  %[[phi:.*]] = phi i1 [ true, {{.*}} ], [ false, {{.*}} ]
+
+; CHECK: %[[gep0:.*]] = getelementptr inbounds i1, i1* %[[load]], i64 0
+; CHECK: store i1 %[[phi]], i1* %[[gep0]], align 4
+
+; CHECK: %[[gep1:.*]] = getelementptr inbounds i1, i1* %[[load]], i64 0
+; CHECK: store i1 %[[phi]], i1* %[[gep1]], align 4