From f405c683ba929fcd0bcaa435ca2fbe4bb221d04b Mon Sep 17 00:00:00 2001
From: Steven Perron <stevenperron@google.com>
Date: Wed, 30 Oct 2024 11:19:23 -0400
Subject: [PATCH] [OPT] Search whole BB for convergence token. (#112728)

The spec for llvm.experimental.convergence.entry says that is must be in
the entry block for a function, and must preceed any other convergent
operation. It does not have to be the first instruction in the entry
block.

Inlining assumes that the call to llvm.experimental.convergence.entry
will be the first instruction after any phi instructions. This commit
modifies inlining to search the entire block for the call.
---
 llvm/lib/Transforms/Utils/InlineFunction.cpp  | 38 ++++++++++---------
 .../Transforms/Inline/convergence-inline.ll   | 24 ++++++++++++
 2 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 4ad426285ce2..a27cb4dd219c 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -181,9 +181,21 @@ namespace {
       }
     }
   };
-
 } // end anonymous namespace
 
+static IntrinsicInst *getConvergenceEntry(BasicBlock &BB) {
+  auto *I = BB.getFirstNonPHI();
+  while (I) {
+    if (auto *IntrinsicCall = dyn_cast<ConvergenceControlInst>(I)) {
+      if (IntrinsicCall->isEntry()) {
+        return IntrinsicCall;
+      }
+    }
+    I = I->getNextNode();
+  }
+  return nullptr;
+}
+
 /// Get or create a target for the branch from ResumeInsts.
 BasicBlock *LandingPadInliningInfo::getInnerResumeDest() {
   if (InnerResumeDest) return InnerResumeDest;
@@ -2496,15 +2508,10 @@ llvm::InlineResult llvm::InlineFunction(CallBase &CB, InlineFunctionInfo &IFI,
   // fully implements convergence control tokens, there is no mixing of
   // controlled and uncontrolled convergent operations in the whole program.
   if (CB.isConvergent()) {
-    auto *I = CalledFunc->getEntryBlock().getFirstNonPHI();
-    if (auto *IntrinsicCall = dyn_cast<IntrinsicInst>(I)) {
-      if (IntrinsicCall->getIntrinsicID() ==
-          Intrinsic::experimental_convergence_entry) {
-        if (!ConvergenceControlToken) {
-          return InlineResult::failure(
-              "convergent call needs convergencectrl operand");
-        }
-      }
+    if (!ConvergenceControlToken &&
+        getConvergenceEntry(CalledFunc->getEntryBlock())) {
+      return InlineResult::failure(
+          "convergent call needs convergencectrl operand");
     }
   }
 
@@ -2795,13 +2802,10 @@ llvm::InlineResult llvm::InlineFunction(CallBase &CB, InlineFunctionInfo &IFI,
   }
 
   if (ConvergenceControlToken) {
-    auto *I = FirstNewBlock->getFirstNonPHI();
-    if (auto *IntrinsicCall = dyn_cast<IntrinsicInst>(I)) {
-      if (IntrinsicCall->getIntrinsicID() ==
-          Intrinsic::experimental_convergence_entry) {
-        IntrinsicCall->replaceAllUsesWith(ConvergenceControlToken);
-        IntrinsicCall->eraseFromParent();
-      }
+    IntrinsicInst *IntrinsicCall = getConvergenceEntry(*FirstNewBlock);
+    if (IntrinsicCall) {
+      IntrinsicCall->replaceAllUsesWith(ConvergenceControlToken);
+      IntrinsicCall->eraseFromParent();
     }
   }
 
diff --git a/llvm/test/Transforms/Inline/convergence-inline.ll b/llvm/test/Transforms/Inline/convergence-inline.ll
index 8c67e6a59b7d..4996a2376be6 100644
--- a/llvm/test/Transforms/Inline/convergence-inline.ll
+++ b/llvm/test/Transforms/Inline/convergence-inline.ll
@@ -185,6 +185,30 @@ define void @test_two_calls() convergent {
   ret void
 }
 
+define i32 @token_not_first(i32 %x) convergent alwaysinline {
+; CHECK-LABEL: @token_not_first(
+; CHECK-NEXT:    {{%.*}} = alloca ptr, align 8
+; CHECK-NEXT:    [[TOKEN:%.*]] = call token @llvm.experimental.convergence.entry()
+; CHECK-NEXT:    [[Y:%.*]] = call i32 @g(i32 [[X:%.*]]) [ "convergencectrl"(token [[TOKEN]]) ]
+; CHECK-NEXT:    ret i32 [[Y]]
+;
+  %p = alloca ptr, align 8
+  %token = call token @llvm.experimental.convergence.entry()
+  %y = call i32 @g(i32 %x) [ "convergencectrl"(token %token) ]
+  ret i32 %y
+}
+
+define void @test_token_not_first() convergent {
+; CHECK-LABEL: @test_token_not_first(
+; CHECK-NEXT:    [[TOKEN:%.*]] = call token @llvm.experimental.convergence.entry()
+; CHECK-NEXT:    {{%.*}} = call i32 @g(i32 23) [ "convergencectrl"(token [[TOKEN]]) ]
+; CHECK-NEXT:    ret void
+;
+  %token = call token @llvm.experimental.convergence.entry()
+  %x = call i32 @token_not_first(i32 23) [ "convergencectrl"(token %token) ]
+  ret void
+}
+
 declare void @f(i32) convergent
 declare i32 @g(i32) convergent