[llvm] [WebAssembly] Correctly consider signext/zext arg flags at function declaration (PR #77281)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-webassembly

Author: Juneyoung Lee (aqjune)

<details>
<summary>Changes</summary>

This patch fixes WebAssembly's FastISel pass to correctly consider signext/zeroext parameter flags at function declaration.
Previously, the flags at call sites were only considered during code generation, which caused an interesting bug report #<!-- -->63388 .
This is problematic especially because in WebAssembly's ABI, either signext or zeroext can be tagged to a function argument, and it must be correctly reflected in the generated code. Unit test https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/WebAssembly/signext-zeroext.ll shows that `i8 zeroext %t` and `i8 signext %t`'s code gen are different.

---
Full diff: https://github.com/llvm/llvm-project/pull/77281.diff


2 Files Affected:

- (modified) llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp (+4-2) 
- (added) llvm/test/CodeGen/WebAssembly/signext-zeroext-callsite.ll (+125) 


``````````diff
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
index 15dc44a0439573..80159974ecd691 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
@@ -839,9 +839,11 @@ bool WebAssemblyFastISel::selectCall(const Instruction *I) {
 
     unsigned Reg;
 
-    if (Attrs.hasParamAttr(I, Attribute::SExt))
+    if (Attrs.hasParamAttr(I, Attribute::SExt) ||
+        (IsDirect && Func->hasParamAttribute(I, Attribute::SExt)))
       Reg = getRegForSignedValue(V);
-    else if (Attrs.hasParamAttr(I, Attribute::ZExt))
+    else if (Attrs.hasParamAttr(I, Attribute::ZExt) ||
+             (IsDirect && Func->hasParamAttribute(I, Attribute::ZExt)))
       Reg = getRegForUnsignedValue(V);
     else
       Reg = getRegForValue(V);
diff --git a/llvm/test/CodeGen/WebAssembly/signext-zeroext-callsite.ll b/llvm/test/CodeGen/WebAssembly/signext-zeroext-callsite.ll
new file mode 100644
index 00000000000000..02ca578716dc98
--- /dev/null
+++ b/llvm/test/CodeGen/WebAssembly/signext-zeroext-callsite.ll
@@ -0,0 +1,125 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -O0 | FileCheck %s
+
+target triple = "wasm32-unknown-unknown"
+
+
+declare i32 @foo(i1 signext noundef, i32 noundef)
+
+; callsite_signext and callsite_nosignext must emit equivalent codes
+
+define i32 @callsite_nosignext() {
+; CHECK-LABEL: callsite_nosignext:
+; CHECK:         .functype callsite_nosignext () -> (i32)
+; CHECK-NEXT:    .local i32, i32, i32, i32, i32, i32
+; CHECK-NEXT:  # %bb.0: # %start
+; CHECK-NEXT:    i32.const 1
+; CHECK-NEXT:    local.set 0
+; CHECK-NEXT:    i32.const 0
+; CHECK-NEXT:    local.set 1
+; CHECK-NEXT:    i32.const 31
+; CHECK-NEXT:    local.set 2
+; CHECK-NEXT:    local.get 0
+; CHECK-NEXT:    local.get 2
+; CHECK-NEXT:    i32.shl
+; CHECK-NEXT:    local.set 3
+; CHECK-NEXT:    local.get 3
+; CHECK-NEXT:    local.get 2
+; CHECK-NEXT:    i32.shr_s
+; CHECK-NEXT:    local.set 4
+; CHECK-NEXT:    local.get 4
+; CHECK-NEXT:    local.get 1
+; CHECK-NEXT:    call foo
+; CHECK-NEXT:    local.set 5
+; CHECK-NEXT:    local.get 5
+; CHECK-NEXT:    return
+start:
+  %0 = call i32 @foo(i1 1, i32 0)
+  ret i32 %0
+}
+
+define i32 @callsite_signext() {
+; CHECK-LABEL: callsite_signext:
+; CHECK:         .functype callsite_signext () -> (i32)
+; CHECK-NEXT:    .local i32, i32, i32, i32, i32, i32
+; CHECK-NEXT:  # %bb.0: # %start
+; CHECK-NEXT:    i32.const 1
+; CHECK-NEXT:    local.set 0
+; CHECK-NEXT:    i32.const 0
+; CHECK-NEXT:    local.set 1
+; CHECK-NEXT:    i32.const 31
+; CHECK-NEXT:    local.set 2
+; CHECK-NEXT:    local.get 0
+; CHECK-NEXT:    local.get 2
+; CHECK-NEXT:    i32.shl
+; CHECK-NEXT:    local.set 3
+; CHECK-NEXT:    local.get 3
+; CHECK-NEXT:    local.get 2
+; CHECK-NEXT:    i32.shr_s
+; CHECK-NEXT:    local.set 4
+; CHECK-NEXT:    local.get 4
+; CHECK-NEXT:    local.get 1
+; CHECK-NEXT:    call foo
+; CHECK-NEXT:    local.set 5
+; CHECK-NEXT:    local.get 5
+; CHECK-NEXT:    return
+start:
+  %0 = call i32 @foo(i1 signext 1, i32 0)
+  ret i32 %0
+}
+
+declare i32 @foo2(i1 zeroext noundef, i32 noundef)
+
+; callsite_zeroext and callsite_nozeroext must emit equivalent codes
+
+define i32 @callsite_nozeroext() {
+; CHECK-LABEL: callsite_nozeroext:
+; CHECK:         .functype callsite_nozeroext () -> (i32)
+; CHECK-NEXT:    .local i32, i32, i32, i32, i32
+; CHECK-NEXT:  # %bb.0: # %start
+; CHECK-NEXT:    i32.const 1
+; CHECK-NEXT:    local.set 0
+; CHECK-NEXT:    i32.const 0
+; CHECK-NEXT:    local.set 1
+; CHECK-NEXT:    i32.const 1
+; CHECK-NEXT:    local.set 2
+; CHECK-NEXT:    local.get 0
+; CHECK-NEXT:    local.get 2
+; CHECK-NEXT:    i32.and
+; CHECK-NEXT:    local.set 3
+; CHECK-NEXT:    local.get 3
+; CHECK-NEXT:    local.get 1
+; CHECK-NEXT:    call foo2
+; CHECK-NEXT:    local.set 4
+; CHECK-NEXT:    local.get 4
+; CHECK-NEXT:    return
+start:
+  %0 = call i32 @foo2(i1 1, i32 0)
+  ret i32 %0
+}
+
+define i32 @callsite_zeroext() {
+; CHECK-LABEL: callsite_zeroext:
+; CHECK:         .functype callsite_zeroext () -> (i32)
+; CHECK-NEXT:    .local i32, i32, i32, i32, i32
+; CHECK-NEXT:  # %bb.0: # %start
+; CHECK-NEXT:    i32.const 1
+; CHECK-NEXT:    local.set 0
+; CHECK-NEXT:    i32.const 0
+; CHECK-NEXT:    local.set 1
+; CHECK-NEXT:    i32.const 1
+; CHECK-NEXT:    local.set 2
+; CHECK-NEXT:    local.get 0
+; CHECK-NEXT:    local.get 2
+; CHECK-NEXT:    i32.and
+; CHECK-NEXT:    local.set 3
+; CHECK-NEXT:    local.get 3
+; CHECK-NEXT:    local.get 1
+; CHECK-NEXT:    call foo2
+; CHECK-NEXT:    local.set 4
+; CHECK-NEXT:    local.get 4
+; CHECK-NEXT:    return
+start:
+  %0 = call i32 @foo2(i1 zeroext 1, i32 0)
+  ret i32 %0
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/77281