[llvm] 167ff52 - [GlobalOpt] Do not shrink global to bool for an unfavorable AS

[Christudasan Devadasan via llvm-commits]

Author: Christudasan Devadasan
Date: 2021-09-16T23:13:30-04:00
New Revision: 167ff5280d7fcad731810d5d2bf10561ed2adacc

URL: https://github.com/llvm/llvm-project/commit/167ff5280d7fcad731810d5d2bf10561ed2adacc
DIFF: https://github.com/llvm/llvm-project/commit/167ff5280d7fcad731810d5d2bf10561ed2adacc.diff

LOG: [GlobalOpt] Do not shrink global to bool for an unfavorable AS

Do not call `TryToShrinkGlobalToBoolean` for address spaces
that don't allow initializers. It inserts an initializer value
while shrinking to bool. Used the target hook introduced with
D109337 to skip this call for the restricted address spaces.

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D109823

Added: 
    llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll

Modified: 
    llvm/lib/Transforms/IPO/GlobalOpt.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index ccf2bfb71c51..bd8f03296e80 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1612,6 +1612,9 @@ processInternalGlobal(GlobalVariable *GV, const GlobalStatus &GS,
 
     Function &StoreFn =
         const_cast<Function &>(*GS.StoredOnceStore->getFunction());
+    bool CanHaveNonUndefGlobalInitializer =
+        GetTTI(StoreFn).canHaveNonUndefGlobalInitializerInAddressSpace(
+            GV->getType()->getAddressSpace());
     // If the initial value for the global was an undef value, and if only
     // one other value was stored into it, we can just change the
     // initializer to be the stored value, then delete all stores to the
@@ -1621,8 +1624,7 @@ processInternalGlobal(GlobalVariable *GV, const GlobalStatus &GS,
     // shared memory (AS 3).
     if (SOVConstant && SOVConstant->getType() == GV->getValueType() &&
         isa<UndefValue>(GV->getInitializer()) &&
-        GetTTI(StoreFn).canHaveNonUndefGlobalInitializerInAddressSpace(
-            GV->getType()->getAddressSpace())) {
+        CanHaveNonUndefGlobalInitializer) {
       // Change the initial value here.
       GV->setInitializer(SOVConstant);
 
@@ -1645,8 +1647,10 @@ processInternalGlobal(GlobalVariable *GV, const GlobalStatus &GS,
       return true;
 
     // Otherwise, if the global was not a boolean, we can shrink it to be a
-    // boolean.
-    if (SOVConstant && GS.Ordering == AtomicOrdering::NotAtomic) {
+    // boolean. Skip this optimization for AS that doesn't allow an initializer.
+    if (SOVConstant && GS.Ordering == AtomicOrdering::NotAtomic &&
+        (!isa<UndefValue>(GV->getInitializer()) ||
+         CanHaveNonUndefGlobalInitializer)) {
       if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
         ++NumShrunkToBool;
         return true;

diff  --git a/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll b/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll
new file mode 100644
index 000000000000..74c35466992b
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/shrink-global-to-bool.ll
@@ -0,0 +1,39 @@
+; RUN: opt -passes=globalopt --mtriple=amdgcn-amd-amdhsa < %s -S | FileCheck %s
+; REQUIRES: amdgpu-registered-target
+
+ at gvar = internal unnamed_addr global i32 undef
+ at lvar = internal unnamed_addr addrspace(3) global i32 undef
+
+; Should optimize @gvar.
+; CHECK-NOT: @gvar
+
+; Negative test for AS(3). Skip shrink global to bool optimization.
+; CHECK: @lvar = internal unnamed_addr addrspace(3) global i32 undef
+
+define void @test_global_var() {
+; CHECK-LABEL: @test_global_var(
+; CHECK:    store volatile i32 10, i32* undef, align 4
+;
+entry:
+  store i32 10, i32* @gvar
+  br label %exit
+exit:
+  %ld = load i32, i32* @gvar
+  store volatile i32 %ld, i32* undef
+  ret void
+}
+
+define void @test_lds_var() {
+; CHECK-LABEL: @test_lds_var(
+; CHECK:    store i32 10, i32 addrspace(3)* @lvar, align 4
+; CHECK:    [[LD:%.*]] = load i32, i32 addrspace(3)* @lvar, align 4
+; CHECK:    store volatile i32 [[LD]], i32* undef, align 4
+;
+entry:
+  store i32 10, i32 addrspace(3)* @lvar
+  br label %exit
+exit:
+  %ld = load i32, i32 addrspace(3)* @lvar
+  store volatile i32 %ld, i32* undef
+  ret void
+}