[WebAssemly] Don't move calls or stores past intervening loads

The register stackifier currently checks for intervening stores (and
loads that may alias them) but doesn't account for the fact that the
instruction being moved may affect intervening loads.

Differential Revision: http://reviews.llvm.org/D17298

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261014 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp b/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
index e23066c..9108b42 100644 (file)
--- a/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
@@ -129,6 +129,7 @@ static bool IsSafeToMove(const MachineInstr *Def, const MachineInstr *Insert,
       return false;
   }
 
+  SawStore = Def->isCall() || Def->mayStore();
   // Check for memory dependencies and side effects.
   for (--I; I != D; --I)
     SawSideEffects |= !I->isSafeToMove(&AA, SawStore);

diff --git a/test/CodeGen/WebAssembly/reg-stackify.ll b/test/CodeGen/WebAssembly/reg-stackify.ll
index 7cc467c..82e5d43 100644 (file)
--- a/test/CodeGen/WebAssembly/reg-stackify.ll
+++ b/test/CodeGen/WebAssembly/reg-stackify.ll
@@ -308,4 +308,43 @@ bb21:                                             ; preds = %bb17, %bb5
   br label %bb5
 }
 
+; Don't move calls past loads
+; CHECK-LABEL: no_stackify_call_past_load:
+; CHECK: i32.call $0=, red
+; CHECK: i32.const $push0=, 0
+; CHECK: i32.load $1=, count($pop0)
+@count = hidden global i32 0, align 4
+define i32 @no_stackify_call_past_load() {
+  %a = call i32 @red()
+  %b = load i32, i32* @count, align 4
+  call i32 @callee(i32 %a)
+  ret i32 %b
+  ; use of a
+}
+
+; Don't move stores past loads if there may be aliasing
+; CHECK-LABEL: no_stackify_store_past_load
+; CHECK: i32.store {{.*}}, 0($1), $0
+; CHECK: i32.load {{.*}}, 0($2)
+; CHECK: i32.call {{.*}}, callee@FUNCTION, $0
+define i32 @no_stackify_store_past_load(i32 %a, i32* %p1, i32* %p2) {
+  store i32 %a, i32* %p1
+  %b = load i32, i32* %p2, align 4
+  call i32 @callee(i32 %a)
+  ret i32 %b
+}
+
+; Can still stackify past invariant loads.
+; CHECK-LABEL: store_past_invar_load
+; CHECK: i32.store $push{{.*}}, 0($1), $0
+; CHECK: i32.call {{.*}}, callee@FUNCTION, $pop
+; CHECK: i32.load $push{{.*}}, 0($2)
+; CHECK: return $pop
+define i32 @store_past_invar_load(i32 %a, i32* %p1, i32* dereferenceable(4) %p2) {
+  store i32 %a, i32* %p1
+  %b = load i32, i32* %p2, !invariant.load !0
+  call i32 @callee(i32 %a)
+  ret i32 %b
+}
+
 !0 = !{}