[NVPTX] Fix internal indirect call prototypes not obeying the ABI

Summary:
The NVPTX backend optimizes the ABI for functions that are internal,
however, this is not legal for indirect call prototypes. Previously, we
would modify the ABI on an aggregate byval type passed to an indirect
call prototype, which would make PTXAS error. This patch just passes the
function as a nullptr to force strict ABI compliance without
modification in the helper function.

Fixes #100055

Author: jhuber6

libc/config/gpu/entrypoints.txt

@@ -1,13 +1,3 @@
-if(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
-  set(extra_entrypoints
-      # stdio.h entrypoints
-      libc.src.stdio.snprintf
-      libc.src.stdio.sprintf
-      libc.src.stdio.vsnprintf
-      libc.src.stdio.vsprintf
-  )
-endif()
-
 set(TARGET_LIBC_ENTRYPOINTS
     # assert.h entrypoints
     libc.src.assert.__assert_fail
@@ -186,13 +176,16 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.errno.errno
 
     # stdio.h entrypoints
-    ${extra_entrypoints}
     libc.src.stdio.clearerr
     libc.src.stdio.fclose
     libc.src.stdio.printf
     libc.src.stdio.vprintf
     libc.src.stdio.fprintf
     libc.src.stdio.vfprintf
+    libc.src.stdio.snprintf
+    libc.src.stdio.sprintf
+    libc.src.stdio.vsnprintf
+    libc.src.stdio.vsprintf
     libc.src.stdio.feof
     libc.src.stdio.ferror
     libc.src.stdio.fflush

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

@@ -1429,7 +1429,6 @@ std::string NVPTXTargetLowering::getPrototype(
 
   bool first = true;
 
-  const Function *F = CB.getFunction();
   unsigned NumArgs = VAInfo ? VAInfo->first : Args.size();
   for (unsigned i = 0, OIdx = 0; i != NumArgs; ++i, ++OIdx) {
     Type *Ty = Args[i].Ty;
@@ -1471,10 +1470,11 @@ std::string NVPTXTargetLowering::getPrototype(
       continue;
     }
 
+    // Indirect calls need strict ABI alignment so we disable optimizations.
     Type *ETy = Args[i].IndirectType;
     Align InitialAlign = Outs[OIdx].Flags.getNonZeroByValAlign();
     Align ParamByValAlign =
-        getFunctionByValParamAlign(F, ETy, InitialAlign, DL);
+        getFunctionByValParamAlign(/*F=*/nullptr, ETy, InitialAlign, DL);
 
     O << ".param .align " << ParamByValAlign.value() << " .b8 ";
     O << "_";

llvm/test/CodeGen/NVPTX/indirect_byval.ll

@@ -0,0 +1,94 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -march=nvptx64 -mcpu=sm_52 -mattr=+ptx64 | FileCheck %s
+; RUN: %if ptxas %{ llc < %s -march=nvptx64 -mcpu=sm_52 -mattr=+ptx64 | %ptxas-verify %}
+
+target triple = "nvptx64-nvidia-cuda"
+
+%struct.S = type { i8 }
+%struct.U = type { i64 }
+
+@ptr = external global ptr, align 8
+
+define internal i32 @foo() {
+; CHECK-LABEL: foo(
+; CHECK:       {
+; CHECK-NEXT:    .local .align 1 .b8 __local_depot0[2];
+; CHECK-NEXT:    .reg .b64 %SP;
+; CHECK-NEXT:    .reg .b64 %SPL;
+; CHECK-NEXT:    .reg .b16 %rs<2>;
+; CHECK-NEXT:    .reg .b32 %r<3>;
+; CHECK-NEXT:    .reg .b64 %rd<3>;
+; CHECK-EMPTY:
+; CHECK-NEXT:  // %bb.0: // %entry
+; CHECK-NEXT:    mov.u64 %SPL, __local_depot0;
+; CHECK-NEXT:    cvta.local.u64 %SP, %SPL;
+; CHECK-NEXT:    ld.global.u64 %rd1, [ptr];
+; CHECK-NEXT:    ld.u8 %rs1, [%SP+1];
+; CHECK-NEXT:    add.u64 %rd2, %SP, 0;
+; CHECK-NEXT:    { // callseq 0, 0
+; CHECK-NEXT:    .param .align 1 .b8 param0[1];
+; CHECK-NEXT:    st.param.b8 [param0+0], %rs1;
+; CHECK-NEXT:    .param .b64 param1;
+; CHECK-NEXT:    st.param.b64 [param1+0], %rd2;
+; CHECK-NEXT:    .param .b32 retval0;
+; CHECK-NEXT:    prototype_0 : .callprototype (.param .b32 _) _ (.param .align 1 .b8 _[1], .param .b64 _);
+; CHECK-NEXT:    call (retval0),
+; CHECK-NEXT:    %rd1,
+; CHECK-NEXT:    (
+; CHECK-NEXT:    param0,
+; CHECK-NEXT:    param1
+; CHECK-NEXT:    )
+; CHECK-NEXT:    , prototype_0;
+; CHECK-NEXT:    ld.param.b32 %r1, [retval0+0];
+; CHECK-NEXT:    } // callseq 0
+; CHECK-NEXT:    st.param.b32 [func_retval0+0], %r1;
+; CHECK-NEXT:    ret;
+entry:
+  %s = alloca %struct.S, align 1
+  %agg.tmp = alloca %struct.S, align 1
+  %0 = load ptr, ptr @ptr, align 8
+  %call = call i32 %0(ptr byval(%struct.S) align 1 %agg.tmp, ptr noundef %s)
+  ret i32 %call
+}
+
+define internal i32 @bar() {
+; CHECK-LABEL: bar(
+; CHECK:         // @bar
+; CHECK-NEXT:  {
+; CHECK-NEXT:    .local .align 8 .b8 __local_depot1[16];
+; CHECK-NEXT:    .reg .b64 %SP;
+; CHECK-NEXT:    .reg .b64 %SPL;
+; CHECK-NEXT:    .reg .b32 %r<3>;
+; CHECK-NEXT:    .reg .b64 %rd<4>;
+; CHECK-EMPTY:
+; CHECK-NEXT:  // %bb.0: // %entry
+; CHECK-NEXT:    mov.u64 %SPL, __local_depot1;
+; CHECK-NEXT:    cvta.local.u64 %SP, %SPL;
+; CHECK-NEXT:    ld.global.u64 %rd1, [ptr];
+; CHECK-NEXT:    ld.u64 %rd2, [%SP+8];
+; CHECK-NEXT:    add.u64 %rd3, %SP, 0;
+; CHECK-NEXT:    { // callseq 1, 0
+; CHECK-NEXT:    .param .align 8 .b8 param0[8];
+; CHECK-NEXT:    st.param.b64 [param0+0], %rd2;
+; CHECK-NEXT:    .param .b64 param1;
+; CHECK-NEXT:    st.param.b64 [param1+0], %rd3;
+; CHECK-NEXT:    .param .b32 retval0;
+; CHECK-NEXT:    prototype_1 : .callprototype (.param .b32 _) _ (.param .align 8 .b8 _[8], .param .b64 _);
+; CHECK-NEXT:    call (retval0),
+; CHECK-NEXT:    %rd1,
+; CHECK-NEXT:    (
+; CHECK-NEXT:    param0,
+; CHECK-NEXT:    param1
+; CHECK-NEXT:    )
+; CHECK-NEXT:    , prototype_1;
+; CHECK-NEXT:    ld.param.b32 %r1, [retval0+0];
+; CHECK-NEXT:    } // callseq 1
+; CHECK-NEXT:    st.param.b32 [func_retval0+0], %r1;
+; CHECK-NEXT:    ret;
+entry:
+  %s = alloca %struct.U, align 8
+  %agg.tmp = alloca %struct.U, align 8
+  %0 = load ptr, ptr @ptr, align 8
+  %call = call noundef i32 %0(ptr byval(%struct.U) align 8 %agg.tmp, ptr %s)
+  ret i32 %call
+}