[PATCH 08/27] [noalias] EarlyCSE: learn about noalias intrinsics

[jeroen.dobbelaere]

Summary

This is part of the series started by D68484.

Note: this is a stable point and tests should run fine with the patches applied up to this point.
Note: D68494 has been incorporated.

[lebedev.ri]

Looks ok.

llvm/lib/Transforms/Scalar/EarlyCSE.cpp

939

"EarlyCSE skipping noalias intrinsic: " ?

[jeroen.dobbelaere]

Adapt to changed rebase in D68494

[jeroen.dobbelaere]

Rebased

[jeroen.dobbelaere]

Rebased to c06b7e2ab5167ad031745a706204abed1aefd823 (July 14, 2020)

[jeroen.dobbelaere]

Rebased to 9fb46a452d4e5666828c95610ceac8dcd9e4ce16 (September 7, 2020)

[jeroen.dobbelaere]

Rebased to f8dbd61074176bae92ec360a093ac7bc498c9321.

llvm/lib/Transforms/Scalar/EarlyCSE.cpp

for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
     if (match(Inst, m_Intrinsic<Intrinsic::assume>())) {
       auto *CondI =
           dyn_cast<Instruction>(cast<CallInst>(Inst)->getArgOperand(0));
       if (CondI && SimpleValue::canHandle(CondI)) {
         LLVM_DEBUG(dbgs() << "EarlyCSE considering assumption: " << *Inst
                           << '\n');
         AvailableValues.insert(CondI, ConstantInt::getTrue(BB->getContext()));
       } else
-        LLVM_DEBUG(dbgs() << "EarlyCSE skipping assumption: " << *Inst << '\n');
+        LLVM_DEBUG(dbgs() << "EarlyCSE skipping intrinsic: " << *Inst << '\n');
       continue;
     }
 
-    // Skip sideeffect intrinsics, for the same reason as assume intrinsics.
     // Likewise, noalias intrinsics don't actually write.
-    if (match(Inst, m_CombineOr(m_Intrinsic<Intrinsic::sideeffect>(),
-                                m_Intrinsic<Intrinsic::noalias>()))) {
-      LLVM_DEBUG(dbgs() << "EarlyCSE skipping intrinsic: " << *Inst << '\n');
+    if (match(Inst, m_Intrinsic<Intrinsic::noalias>()) ||
+        match(Inst, m_Intrinsic<Intrinsic::noalias_decl>()) ||
+        match(Inst, m_Intrinsic<Intrinsic::side_noalias>()) ||
+        match(Inst, m_Intrinsic<Intrinsic::noalias_arg_guard>())) {
+      LLVM_DEBUG(dbgs() << "EarlyCSE skipping noalias intrinsic: " << *Inst
+                        << '\n');
+      continue;
+    }
+
+    // Skip sideeffect intrinsics, for the same reason as assume intrinsics.
+    if (match(Inst, m_Intrinsic<Intrinsic::sideeffect>())) {
+      LLVM_DEBUG(dbgs() << "EarlyCSE skipping sideeffect: " << *Inst << '\n');
       continue;
     }
 
     // We can skip all invariant.start intrinsics since they only read memory,
     // and we can forward values across it. For invariant starts without
     // invariant ends, we can use the fact that the invariantness never ends to
     // start a scope in the current generaton which is true for all future
     // generations.  Also, we dont need to consume the last store since the

llvm/test/Transforms/EarlyCSE/basic.ll

define i32 @test2a(i32 *%P, i1 %b) {
   %Diff = sub i32 %V1, %V2
   ret i32 %Diff
   ; CHECK: ret i32 0
 }
 
 ; CHECK-LABEL: @test2b(
 define i32 @test2b(i32 *%P, i1 %b) {
   %V1 = load i32, i32* %P
-  call i8* @llvm.noalias.p0i8(i8* undef, metadata !1)
+  call i8* @llvm.noalias.p0i8.p0i8.p0p0i8.i32(i8* undef, i8* null, i8** null, i32 0, metadata !1)
+  %V2 = load i32, i32* %P
+  %Diff = sub i32 %V1, %V2
+  ret i32 %Diff
+  ; CHECK: ret i32 0
+}
+
+; CHECK-LABEL: @test2c(
+define i32 @test2c(i32 *%P, i1 %b) {
+  %V1 = load i32, i32* %P
+  call i8* @llvm.side.noalias.p0i8.p0i8.p0p0i8.p0p0i8.i32(i8* undef, i8* null, i8** null, i8** null, i32 0, metadata !1)
   %V2 = load i32, i32* %P
   %Diff = sub i32 %V1, %V2
   ret i32 %Diff
   ; CHECK: ret i32 0
 }
 
 ;; Cross block load value numbering.
 ; CHECK-LABEL: @test3(
define i32 @test6a(i32 *%P, i1 %b) {
   %V1 = load i32, i32* %P
   ret i32 %V1
   ; CHECK: ret i32 42
 }
 
 ; CHECK-LABEL: @test6b(
 define i32 @test6b(i32 *%P, i1 %b) {
   store i32 42, i32* %P
-  call i8* @llvm.noalias.p0i8(i8* undef, metadata !1)
+  call i8* @llvm.noalias.p0i8.p0i8.p0p0i8.i32(i8* undef, i8* null, i8** null, i32 0, metadata !1)
+  %V1 = load i32, i32* %P
+  ret i32 %V1
+  ; CHECK: ret i32 42
+}
+
+; CHECK-LABEL: @test6c(
+define i32 @test6c(i32 *%P, i1 %b) {
+  store i32 42, i32* %P
+  call i8* @llvm.side.noalias.p0i8.p0i8.p0p0i8.p0p0i8.i32(i8* undef, i8* null, i8** null, i8** null, i32 0, metadata !1)
   %V1 = load i32, i32* %P
   ret i32 %V1
   ; CHECK: ret i32 42
 }
 
 ;; Trivial dead store elimination.
 ; CHECK-LABEL: @test7(
 define void @test7(i32 *%P) {

 ; CHECK: store i32 2, i32* @c, align 4
   %load = load i32, i32* @c, align 4
   store i32 0, i32* @c, align 4
   %call = call i32 @reads_c(i32 0)
   store i32 2, i32* @c, align 4
   ret void
 }
 
-declare i8* @llvm.noalias.p0i8(i8*, metadata) nounwind
+declare i8*  @llvm.noalias.p0i8.p0i8.p0p0i8.i32(i8*, i8*, i8**, i32, metadata ) nounwind
+declare i8*  @llvm.side.noalias.p0i8.p0i8.p0p0i8.p0p0i8.i32(i8*, i8*, i8**, i8**, i32, metadata ) nounwind
 
 !0 = !{!0, !"some domain"}
 !1 = !{!1, !0, !"some scope"}