From: Heejin Ahn <aheejin@gmail.com>
Date: Thu, 10 Jan 2019 23:12:07 +0000 (+0000)
Subject: [WebAssembly] Fix stack pointer store check in RegStackify
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d5697a92c2eb244f7cba4102228f146fd8e9c1dc;p=llvm

[WebAssembly] Fix stack pointer store check in RegStackify

Summary:
We now use __stack_pointer global and global.get/global.set instruction.
This fixes the checking routine for stack_pointer writes accordingly.

This also fixes the existing __stack_pointer test in reg-stackify.ll:
That test used to pass not because of __stack_pointer clashes but
because the function `stackpointer_callee` was not marked as `readnone`,
so it was assumed to possibly write to memory arbitraily, and
`global.set` instruction was marked as `mayStore` in the .td definition,
so they were identified as intervening writes. After we added `readnone`
to its attribute, this test fails without this patch.

Reviewers: dschuff, sunfish

Subscribers: jgravelle-google, sbc100, llvm-commits

Differential Revision: https://reviews.llvm.org/D56094

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350906 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp b/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
index ceb024b4be0..e991bf47e07 100644
--- a/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
@@ -181,19 +181,6 @@ static void Query(const MachineInstr &MI, AliasAnalysis &AA, bool &Read,
   // Check for stores.
   if (MI.mayStore()) {
     Write = true;
-
-    // Check for stores to __stack_pointer.
-    for (auto MMO : MI.memoperands()) {
-      const MachinePointerInfo &MPI = MMO->getPointerInfo();
-      if (MPI.V.is<const PseudoSourceValue *>()) {
-        auto PSV = MPI.V.get<const PseudoSourceValue *>();
-        if (const ExternalSymbolPseudoSourceValue *EPSV =
-                dyn_cast<ExternalSymbolPseudoSourceValue>(PSV))
-          if (StringRef(EPSV->getSymbol()) == "__stack_pointer") {
-            StackPointer = true;
-          }
-      }
-    }
   } else if (MI.hasOrderedMemoryRef()) {
     switch (MI.getOpcode()) {
     case WebAssembly::DIV_S_I32:
@@ -258,6 +245,11 @@ static void Query(const MachineInstr &MI, AliasAnalysis &AA, bool &Read,
     }
   }
 
+  // Check for writes to __stack_pointer global.
+  if (MI.getOpcode() == WebAssembly::GLOBAL_SET_I32 &&
+      strcmp(MI.getOperand(0).getSymbolName(), "__stack_pointer") == 0)
+    StackPointer = true;
+
   // Analyze calls.
   if (MI.isCall()) {
     unsigned CalleeOpNo = WebAssembly::getCalleeOpNo(MI);
diff --git a/test/CodeGen/WebAssembly/reg-stackify.ll b/test/CodeGen/WebAssembly/reg-stackify.ll
index 2b36ba0e3ef..6b4487bc66f 100644
--- a/test/CodeGen/WebAssembly/reg-stackify.ll
+++ b/test/CodeGen/WebAssembly/reg-stackify.ll
@@ -634,7 +634,7 @@ bb10:                                             ; preds = %bb9, %bb
 ; NOREGS-LABEL: stackpointer_dependency:
 ; NOREGS:      call stackpointer_callee@FUNCTION
 ; NOREGS:      global.set __stack_pointer
-declare i32 @stackpointer_callee(i8* readnone, i8* readnone)
+declare i32 @stackpointer_callee(i8* readnone, i8* readnone) nounwind readnone
 declare i8* @llvm.frameaddress(i32)
 define i32 @stackpointer_dependency(i8* readnone) {
   %2 = tail call i8* @llvm.frameaddress(i32 0)