[llvm] [SDAG] Read-only intrinsics must have WillReturn attribute to be treated as loads (PR #99999)

[Kevin McAfee via llvm-commits]

https://github.com/kalxr updated https://github.com/llvm/llvm-project/pull/99999

>From 1e83b39f1c5620cd986b3d2238ef80ad5a642c46 Mon Sep 17 00:00:00 2001
From: Kevin McAfee <kmcafee at nvidia.com>
Date: Mon, 22 Jul 2024 15:53:56 -0700
Subject: [PATCH 1/3] [SDAG] Read-only intrinsics must have WillReturn to be
 treated as loads

---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 9f5e6466309e9..162ef5b159fb9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5225,7 +5225,7 @@ void SelectionDAGBuilder::visitTargetIntrinsic(const CallInst &I,
   // definition.
   const Function *F = I.getCalledFunction();
   bool HasChain = !F->doesNotAccessMemory();
-  bool OnlyLoad = HasChain && F->onlyReadsMemory();
+  bool OnlyLoad = HasChain && F->onlyReadsMemory() && F->willReturn();
 
   // Build the operand list.
   SmallVector<SDValue, 8> Ops;

>From fa37027fe1b0c930ae4b83b6ca4835797fa719e3 Mon Sep 17 00:00:00 2001
From: Kevin McAfee <kmcafee at nvidia.com>
Date: Mon, 22 Jul 2024 16:00:46 -0700
Subject: [PATCH 2/3] Update BPF test instruction order

---
 llvm/test/CodeGen/BPF/intrinsics.ll         | 8 ++++----
 llvm/test/CodeGen/BPF/objdump_intrinsics.ll | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/llvm/test/CodeGen/BPF/intrinsics.ll b/llvm/test/CodeGen/BPF/intrinsics.ll
index 0f59fd5604732..8331ee5ff04ee 100644
--- a/llvm/test/CodeGen/BPF/intrinsics.ll
+++ b/llvm/test/CodeGen/BPF/intrinsics.ll
@@ -31,10 +31,10 @@ define i32 @ld_h(ptr %ctx, ptr %ctx2, i32 %foo) #0 {
   %5 = trunc i64 %4 to i32
   ret i32 %5
 ; CHECK-LABEL: ld_h:
-; CHECK-EL: r0 = *(u16 *)skb[r
 ; CHECK-EL: r0 = *(u16 *)skb[123]
-; CHECK-EB: r0 = *(u16 *)skb[r
+; CHECK-EL: r0 = *(u16 *)skb[r
 ; CHECK-EB: r0 = *(u16 *)skb[123]
+; CHECK-EB: r0 = *(u16 *)skb[r
 }
 
 declare i64 @llvm.bpf.load.half(ptr, i64) #1
@@ -48,10 +48,10 @@ define i32 @ld_w(ptr %ctx, ptr %ctx2, i32 %foo) #0 {
   %5 = trunc i64 %4 to i32
   ret i32 %5
 ; CHECK-LABEL: ld_w:
-; CHECK-EL: r0 = *(u32 *)skb[r
 ; CHECK-EL: r0 = *(u32 *)skb[123]
-; CHECK-EB: r0 = *(u32 *)skb[r
+; CHECK-EL: r0 = *(u32 *)skb[r
 ; CHECK-EB: r0 = *(u32 *)skb[123]
+; CHECK-EB: r0 = *(u32 *)skb[r
 }
 
 declare i64 @llvm.bpf.load.word(ptr, i64) #1
diff --git a/llvm/test/CodeGen/BPF/objdump_intrinsics.ll b/llvm/test/CodeGen/BPF/objdump_intrinsics.ll
index 92db0882398b6..5497fce989d21 100644
--- a/llvm/test/CodeGen/BPF/objdump_intrinsics.ll
+++ b/llvm/test/CodeGen/BPF/objdump_intrinsics.ll
@@ -31,10 +31,10 @@ define i32 @ld_h(ptr %ctx, ptr %ctx2, i32 %foo) #0 {
   %5 = trunc i64 %4 to i32
   ret i32 %5
 ; CHECK-LABEL: ld_h:
-; CHECK-EL: r0 = *(u16 *)skb[r
 ; CHECK-EL: r0 = *(u16 *)skb[123]
-; CHECK-EB: r0 = *(u16 *)skb[r
+; CHECK-EL: r0 = *(u16 *)skb[r
 ; CHECK-EB: r0 = *(u16 *)skb[123]
+; CHECK-EB: r0 = *(u16 *)skb[r
 }
 
 declare i64 @llvm.bpf.load.half(ptr, i64) #1
@@ -48,10 +48,10 @@ define i32 @ld_w(ptr %ctx, ptr %ctx2, i32 %foo) #0 {
   %5 = trunc i64 %4 to i32
   ret i32 %5
 ; CHECK-LABEL: ld_w:
-; CHECK-EL: r0 = *(u32 *)skb[r
 ; CHECK-EL: r0 = *(u32 *)skb[123]
-; CHECK-EB: r0 = *(u32 *)skb[r
+; CHECK-EL: r0 = *(u32 *)skb[r
 ; CHECK-EB: r0 = *(u32 *)skb[123]
+; CHECK-EB: r0 = *(u32 *)skb[r
 }
 
 declare i64 @llvm.bpf.load.word(ptr, i64) #1

>From 7b43cc56c7857bf88d5835e0c54fcc75e1caac26 Mon Sep 17 00:00:00 2001
From: Kevin McAfee <kmcafee at nvidia.com>
Date: Wed, 31 Jul 2024 14:52:03 -0700
Subject: [PATCH 3/3] Temp assert to find tests with non-WillReturn intrinsics

---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 162ef5b159fb9..986841302e9c4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5227,6 +5227,9 @@ void SelectionDAGBuilder::visitTargetIntrinsic(const CallInst &I,
   bool HasChain = !F->doesNotAccessMemory();
   bool OnlyLoad = HasChain && F->onlyReadsMemory() && F->willReturn();
 
+  bool PrevOnlyLoad = HasChain && F->onlyReadsMemory();
+  assert((!PrevOnlyLoad || F->willReturn()) && "Intrinsic treated as `OnlyLoad` despite no WillReturn");
+
   // Build the operand list.
   SmallVector<SDValue, 8> Ops;
   if (HasChain) {  // If this intrinsic has side-effects, chainify it.