AMDGPU: Fix -amdgpu-mfma-vgpr-form flag on gfx908

[arsenm]

This should be ignored since there are no VGPR forms. This
makes it possible to flip the default for the flag to true.

[arsenm]

• AMDGPU: Fix -amdgpu-mfma-vgpr-form flag on gfx908 #150599 👈 (View in Graphite)
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[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Matt Arsenault (arsenm)

Changes

This should be ignored since there are no VGPR forms. This
makes it possible to flip the default for the flag to true.

---

Full diff: https://github.com/llvm/llvm-project/pull/150599.diff

2 Files Affected:

• (modified) llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp (+9-5)
• (modified) llvm/test/CodeGen/AMDGPU/gfx90a-enc.ll (+3)

diff --git a/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
index f0be204cd9bdb..9a1448f1f95dc 100644
--- a/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
@@ -81,11 +81,15 @@ SIMachineFunctionInfo::SIMachineFunctionInfo(const Function &F,
     PSInputAddr = AMDGPU::getInitialPSInputAddr(F);
   }
 
-  MayNeedAGPRs = ST.hasMAIInsts() && !MFMAVGPRForm;
-  if (!MFMAVGPRForm && ST.hasGFX90AInsts() &&
-      ST.getMaxNumVGPRs(F) <= AMDGPU::VGPR_32RegClass.getNumRegs() &&
-      !mayUseAGPRs(F))
-    MayNeedAGPRs = false; // We will select all MAI with VGPR operands.
+  MayNeedAGPRs = ST.hasMAIInsts();
+  if (ST.hasGFX90AInsts()) {
+    // FIXME: MayNeedAGPRs is a misnomer for how this is used. MFMA selection
+    // should be separated from availability of AGPRs
+    if (MFMAVGPRForm ||
+        (ST.getMaxNumVGPRs(F) <= AMDGPU::VGPR_32RegClass.getNumRegs() &&
+         !mayUseAGPRs(F)))
+      MayNeedAGPRs = false; // We will select all MAI with VGPR operands.
+  }
 
   if (AMDGPU::isChainCC(CC)) {
     // Chain functions don't receive an SP from their caller, but are free to
diff --git a/llvm/test/CodeGen/AMDGPU/gfx90a-enc.ll b/llvm/test/CodeGen/AMDGPU/gfx90a-enc.ll
index 99690e407d8da..fe8edd5d60912 100644
--- a/llvm/test/CodeGen/AMDGPU/gfx90a-enc.ll
+++ b/llvm/test/CodeGen/AMDGPU/gfx90a-enc.ll
@@ -1,4 +1,7 @@
 ; RUN: llc -mtriple=amdgcn -mcpu=gfx908 -show-mc-encoding < %s | FileCheck -check-prefixes=GFX9,GFX908 %s
+
+; Make sure flag is ignored
+; RUN: llc -mtriple=amdgcn -mcpu=gfx908 -amdgpu-mfma-vgpr-form=1 -show-mc-encoding < %s | FileCheck -check-prefixes=GFX9,GFX908 %s
 ; RUN: llc -mtriple=amdgcn -mcpu=gfx90a -show-mc-encoding < %s | FileCheck -check-prefixes=GFX9,GFX90A %s
 
 ; GFX9-DAG:   buffer_load_format_xyzw v[{{[0-9:]+}}], v{{[0-9]+}}, s[{{[0-9:]+}}], 0 idxen ; encoding:

[llvm-ci]

LLVM Buildbot has detected a new failure on builder llvm-clang-x86_64-expensive-checks-debian running on gribozavr4 while building llvm at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/16/builds/23259

Here is the relevant piece of the build log for the reference

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: TableGen/RuntimeLibcallEmitter.td' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/llvm-tblgen -gen-runtime-libcalls -I /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/../../include /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter.td | /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/FileCheck /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter.td # RUN: at line 1
+ /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/llvm-tblgen -gen-runtime-libcalls -I /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/../../include /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter.td
+ /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/FileCheck /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter.td
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter.td:98:16: error: CHECK-NEXT: expected string not found in input
// CHECK-NEXT: sqrtl_f80 = 7, // sqrtl
               ^
<stdin>:32:23: note: scanning from here
 calloc = 6, // calloc
                      ^
<stdin>:34:2: note: possible intended match here
 sqrtl_f80 = 8, // sqrtl
 ^

Input file: <stdin>
Check file: /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter.td

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           .
           .
           .
          27:  ___memcpy = 1, // ___memcpy 
          28:  ___memset = 2, // ___memset 
          29:  __ashlsi3 = 3, // __ashlsi3 
          30:  __lshrdi3 = 4, // __lshrdi3 
          31:  bzero = 5, // bzero 
          32:  calloc = 6, // calloc 
next:98'0                           X error: no match found
          33:  sqrtl_f128 = 7, // sqrtl 
next:98'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~
          34:  sqrtl_f80 = 8, // sqrtl 
next:98'0     ~~~~~~~~~~~~~~~~~~~~~~~~~
next:98'1      ?                        possible intended match
          35:  NumLibcallImpls = 9 
next:98'0     ~~~~~~~~~~~~~~~~~~~~~
          36: }; 
next:98'0     ~~~
          37: } // End namespace RTLIB 
next:98'0     ~~~~~~~~~~~~~~~~~~~~~~~~~
          38: } // End namespace llvm 
next:98'0     ~~~~~~~~~~~~~~~~~~~~~~~~
          39: #endif 
next:98'0     ~~~~~~~
...