[FastISel] fix a fallback diagnostic.

[igorb]

Summary

FastISel was marked as failed in case instruction selection succeeded.

[igorb]

ping

[zvi]

Is there a way to produce a test to cover this fix?

[ab]

There's a test for the call side in r294970, and I added some tests in r299093, you can probably make either check the generic fastisel fallback diagnostic too?

But in general, it's probably time to replace the function-level fallback diagnostic with the remarks, now that we have both.

@bogner, @qcolombet: do you guys still use the function diagnostic?

[igorb]

• add tests. Thanks.

[zvi]

LGTM

lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

if (FastIS) {
         }
 
         // Bottom-up: reset the insert pos at the top, after any local-value
         // instructions.
         FastIS->recomputeInsertPt();
 
         // Try to select the instruction with FastISel.
         if (FastIS->selectInstruction(Inst)) {
-          FastISelFailed = true;
           --NumFastIselRemaining;
           ++NumFastIselSuccess;
           // If fast isel succeeded, skip over all the folded instructions, and
           // then see if there is a load right before the selected instructions.
           // Try to fold the load if so.
           const Instruction *BeforeInst = Inst;
           while (BeforeInst != &*Begin) {
             BeforeInst = &*std::prev(BasicBlock::const_iterator(BeforeInst));
             if (!isFoldedOrDeadInstruction(BeforeInst, FuncInfo))
               break;
           }
           if (BeforeInst != Inst && isa<LoadInst>(BeforeInst) &&
               BeforeInst->hasOneUse() &&
               FastIS->tryToFoldLoad(cast<LoadInst>(BeforeInst), Inst)) {
             // If we succeeded, don't re-select the load.
             BI = std::next(BasicBlock::const_iterator(BeforeInst));
             --NumFastIselRemaining;
             ++NumFastIselSuccess;
           }
           continue;
         }
 
+        FastISelFailed = true;
+
         // Then handle certain instructions as single-LLVM-Instruction blocks.
         // We cannot separate out GCrelocates to their own blocks since we need
         // to keep track of gc-relocates for a particular gc-statepoint. This is
         // done by SelectionDAGBuilder::LowerAsSTATEPOINT, called before
         // visitGCRelocate.
         if (isa<CallInst>(Inst) && !isStatepoint(Inst) && !isGCRelocate(Inst)) {
           OptimizationRemarkMissed R("sdagisel", "FastISelFailure",
                                      Inst->getDebugLoc(), LLVMBB);

test/CodeGen/X86/fast-isel-abort-warm.ll

-; RUN: llc -fast-isel -o - %s -fast-isel-report-on-fallback 2>&1 | FileCheck %s
+; RUN: llc -fast-isel -o - %s -fast-isel-report-on-fallback -pass-remarks-missed=isel 2>&1 | FileCheck %s
 ; Make sure FastISel report a warming when we asked it to do so.
 ; Note: This test needs to use whatever is not supported by FastISel.
 ;       Thus, this test may fail because inline asm gets supported in FastISel.
 ;       To fix this, use something else that's not supported (e.g., weird types).
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx"
 
+; CHECK: remark: <unknown>:0:0: FastISel missed call:   call void asm sideeffect
 ; CHECK: warning: Instruction selection used fallback path for foo
 define void @foo(){
 entry:
   call void asm sideeffect "nop", "~{dirflag},~{fpsr},~{flags}"()
   ret void
 }
+
+; CHECK: remark: <unknown>:0:0: FastISel missed:   store i128
+; CHECK: warning: Instruction selection used fallback path for test_instruction_fallback
+define void @test_instruction_fallback(i128* %ptr){
+  %v1 = load i128, i128* %ptr
+  %result = add i128 %v1, %v1
+  store i128 %result, i128 * %ptr
+  ret void
+}
+
+; CHECK-NOT: remark: <unknown>:0:0: FastISel missed
+; CHECK-NOT: warning: Instruction selection used fallback path for test_instruction_not_fallback
+define i32 @test_instruction_not_fallback(i32 %a){
+  %result = add i32 %a, %a
+  ret i32 %result
+}