[llvm] r256953 - [WebAssembly] Don't use range-based loop for a list that's being modified

[Dan Gohman via llvm-commits]

Author: djg
Date: Wed Jan  6 12:29:35 2016
New Revision: 256953

URL: http://llvm.org/viewvc/llvm-project?rev=256953&view=rev
Log:
[WebAssembly] Don't use range-based loop for a list that's being modified

The first instruction in a block is what the rend() iterator points to, so
if it moves, we need to re-evaluate rend() so that we continue to iterate
through the rest of the instructions.

Modified:
    llvm/trunk/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
    llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll

Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp?rev=256953&r1=256952&r2=256953&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp Wed Jan  6 12:29:35 2016
@@ -147,8 +147,10 @@ bool WebAssemblyRegStackify::runOnMachin
   // block boundaries, and the blocks aren't ordered so the block visitation
   // order isn't significant, but we may want to change this in the future.
   for (MachineBasicBlock &MBB : MF) {
-    for (MachineInstr &MI : reverse(MBB)) {
-      MachineInstr *Insert = &MI;
+    // Don't use a range-based for loop, because we modify the list as we're
+    // iterating over it and the end iterator may change.
+    for (auto MII = MBB.rbegin(); MII != MBB.rend(); ++MII) {
+      MachineInstr *Insert = &*MII;
       // Don't nest anything inside a phi.
       if (Insert->getOpcode() == TargetOpcode::PHI)
         break;
@@ -221,7 +223,7 @@ bool WebAssemblyRegStackify::runOnMachin
         Insert = Def;
       }
       if (AnyStackified)
-        ImposeStackOrdering(&MI);
+        ImposeStackOrdering(&*MII);
     }
   }
 

Modified: llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll?rev=256953&r1=256952&r2=256953&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll (original)
+++ llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify.ll Wed Jan  6 12:29:35 2016
@@ -93,6 +93,7 @@ back:
 ; Test that a simple loop is handled as expected.
 
 ; CHECK-LABEL: test2:
+; CHECK-NOT: local
 ; CHECK: block BB2_2{{$}}
 ; CHECK: br_if {{[^,]*}}, BB2_2{{$}}
 ; CHECK: BB2_1: