[llvm] Invalidate range metadata when folding bitcast into load (PR #133095)

[via llvm-commits]

https://github.com/LU-JOHN created https://github.com/llvm/llvm-project/pull/133095

When folding bitcast into a load, range metadata may not match new load type.  If so, invalidate the range metadata.

>From ddcaccbbb9734c26eeff5b61502ec329fed55318 Mon Sep 17 00:00:00 2001
From: John Lu <John.Lu at amd.com>
Date: Wed, 26 Mar 2025 09:31:47 -0500
Subject: [PATCH] Invalidate range MD, when folding bitcast into load

Signed-off-by: John Lu <John.Lu at amd.com>
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp |  9 ++++++
 .../test/CodeGen/X86/fold_bitcast_md_range.ll | 31 +++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 llvm/test/CodeGen/X86/fold_bitcast_md_range.ll

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index bf49642634291..a8e516b8c2937 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -15964,6 +15964,15 @@ SDValue DAGCombiner::visitBITCAST(SDNode *N) {
 
     if (TLI.isLoadBitCastBeneficial(N0.getValueType(), VT, DAG,
                                     *LN0->getMemOperand())) {
+      // If the range metadata type does not match the new memory
+      // operation type, remove the range metadata.
+      if (const MDNode *MD = LN0->getRanges()) {
+        ConstantInt *Lower = mdconst::extract<ConstantInt>(MD->getOperand(0));
+        if (Lower->getBitWidth() != VT.getScalarSizeInBits() ||
+            !VT.isInteger()) {
+          LN0->getMemOperand()->clearRanges();
+        }
+      }
       SDValue Load =
           DAG.getLoad(VT, SDLoc(N), LN0->getChain(), LN0->getBasePtr(),
                       LN0->getMemOperand());
diff --git a/llvm/test/CodeGen/X86/fold_bitcast_md_range.ll b/llvm/test/CodeGen/X86/fold_bitcast_md_range.ll
new file mode 100644
index 0000000000000..3417acb4e2744
--- /dev/null
+++ b/llvm/test/CodeGen/X86/fold_bitcast_md_range.ll
@@ -0,0 +1,31 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=x86_64-apple-macosx10.12.0 -O0 < %s | FileCheck %s
+
+; Ensure that when a bitcast is folded into a load, range metadata is invalidated
+; if it does not match the new type.
+
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+
+define void @fold_bitcast_range_metadata() {
+; CHECK-LABEL: fold_bitcast_range_metadata:
+; CHECK:       ## %bb.0: ## %start
+; CHECK-NEXT:    movaps 0, %xmm0
+; CHECK-NEXT:    movaps {{.*#+}} xmm1 = [1,0,0,0]
+; CHECK-NEXT:    pcmpeqb %xmm1, %xmm0
+; CHECK-NEXT:    pmovmskb %xmm0, %eax
+; CHECK-NEXT:    subl $65535, %eax ## imm = 0xFFFF
+; CHECK-NEXT:    jne LBB0_1
+; CHECK-NEXT:    jmp LBB0_1
+; CHECK-NEXT:  LBB0_1: ## %bb1
+; CHECK-NEXT:    retq
+start:
+  %0 = load i128, ptr null, align 16, !range !0, !noundef !1
+  %1 = icmp eq i128 %0, 1
+  br i1 %1, label %bb1, label %bb1
+
+bb1:                                              ; preds = %start, %start
+  ret void
+}
+
+!0 = !{i128 0, i128 3}
+!1 = !{}