[PATCH] D28170: [LICM] When promoting scalars, allow inserting stores to thread-local allocas

[Michael Kuperstein via Phabricator via llvm-commits]

mkuper created this revision.
mkuper added a reviewer: reames.
mkuper added a subscriber: llvm-commits.

This is similar to the allocfn case - if an alloca is not captured, then it's necessarily thread-local.


https://reviews.llvm.org/D28170

Files:
  lib/Transforms/Scalar/LICM.cpp
  test/Transforms/LICM/promote-tls.ll


Index: test/Transforms/LICM/promote-tls.ll
===================================================================
--- test/Transforms/LICM/promote-tls.ll
+++ test/Transforms/LICM/promote-tls.ll
@@ -12,6 +12,7 @@
 declare i8* @malloc(i64)
 
 ; Exercise the TLS case
+; CHECK-LABEL: @test
 define i32* @test(i32 %n) {
 entry:
   ;; ignore the required null check for simplicity
@@ -49,9 +50,49 @@
   ret i32* null
 }
 
+; Stack allocations can also be thread-local
+; CHECK-LABEL: @test2
+define i32* @test2(i32 %n) {
+entry:
+  ;; ignore the required null check for simplicity
+  %mem = alloca i8, i32 16
+  %addr = bitcast i8* %mem to i32*
+  br label %for.body.lr.ph
+
+for.body.lr.ph:                                   ; preds = %entry
+  br label %for.header
+
+for.header:
+  %i.02 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.body ]
+  %old = load i32, i32* %addr, align 4
+  ; deliberate impossible to analyze branch
+  %guard = load atomic i8*, i8** @p monotonic, align 8
+  %exitcmp = icmp eq i8* %guard, null
+  br i1 %exitcmp, label %for.body, label %early-exit
+
+early-exit:
+; CHECK-LABEL: early-exit:
+; CHECK: store i32 %new1.lcssa, i32* %addr, align 1
+  ret i32* null
+
+for.body:
+  %new = add i32 %old, 1
+  store i32 %new, i32* %addr, align 4
+  %inc = add nsw i32 %i.02, 1
+  %cmp = icmp slt i32 %inc, %n
+  br i1 %cmp, label %for.header, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge:                       ; preds = %for.body
+; CHECK-LABEL: for.cond.for.end_crit_edge:
+; CHECK: store i32 %new.lcssa, i32* %addr, align 1
+  %split = phi i32* [ %addr, %for.body ]
+  ret i32* null
+}
+
 declare i8* @not_malloc(i64)
 
 ; Negative test - not TLS
+; CHECK-LABEL: @test_neg
 define i32* @test_neg(i32 %n) {
 entry:
   ;; ignore the required null check for simplicity
@@ -93,6 +134,7 @@
 
 ; Negative test - can't speculate load since branch
 ; may control alignment
+; CHECK-LABEL: @test_neg2
 define i32* @test_neg2(i32 %n) {
 entry:
   ;; ignore the required null check for simplicity
@@ -131,4 +173,3 @@
   %split = phi i32* [ %addr, %for.body ]
   ret i32* null
 }
-
Index: lib/Transforms/Scalar/LICM.cpp
===================================================================
--- lib/Transforms/Scalar/LICM.cpp
+++ lib/Transforms/Scalar/LICM.cpp
@@ -1034,7 +1034,8 @@
   if (!SafeToInsertStore) {
     Value *Object = GetUnderlyingObject(SomePtr, MDL);
     SafeToInsertStore =
-        isAllocLikeFn(Object, TLI) && !PointerMayBeCaptured(Object, true, true);
+        (isAllocLikeFn(Object, TLI) || isa<AllocaInst>(Object)) &&
+        !PointerMayBeCaptured(Object, true, true);
   }
 
   // If we've still failed to prove we can sink the store, give up.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D28170.82710.patch
Type: text/x-patch
Size: 2694 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20161230/504dee5e/attachment.bin>