[AArch64][LoopIdiom] Disable LoopIdiomTransform when NoImplicitFloat is present (#87677)

This behavior is aligned with both LoopVectorizer and SLPVectorizer.

Author: mshockwave

llvm/lib/Target/AArch64/AArch64LoopIdiomTransform.cpp

@@ -190,17 +190,23 @@ AArch64LoopIdiomTransformPass::run(Loop &L, LoopAnalysisManager &AM,
 bool AArch64LoopIdiomTransform::run(Loop *L) {
   CurLoop = L;
 
-  if (DisableAll || L->getHeader()->getParent()->hasOptSize())
+  Function &F = *L->getHeader()->getParent();
+  if (DisableAll || F.hasOptSize())
     return false;
 
+  if (F.hasFnAttribute(Attribute::NoImplicitFloat)) {
+    LLVM_DEBUG(dbgs() << DEBUG_TYPE << " is disabled on " << F.getName()
+                      << " due to its NoImplicitFloat attribute");
+    return false;
+  }
+
   // If the loop could not be converted to canonical form, it must have an
   // indirectbr in it, just give up.
   if (!L->getLoopPreheader())
     return false;
 
-  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Scanning: F["
-                    << CurLoop->getHeader()->getParent()->getName()
-                    << "] Loop %" << CurLoop->getHeader()->getName() << "\n");
+  LLVM_DEBUG(dbgs() << DEBUG_TYPE " Scanning: F[" << F.getName() << "] Loop %"
+                    << CurLoop->getHeader()->getName() << "\n");
 
   return recognizeByteCompare();
 }

llvm/test/Transforms/LoopIdiom/AArch64/byte-compare-index.ll

@@ -2090,3 +2090,99 @@ while.end:
   ret i32 %res
 }
 
+; The optimization should be disabled when noimplicitfloat is present.
+define i32 @no_implicit_float(ptr %a, ptr %b, i32 %len, i32 %extra, i32 %n) noimplicitfloat {
+; CHECK-LABEL: define i32 @no_implicit_float(
+; CHECK-SAME: ptr [[A:%.*]], ptr [[B:%.*]], i32 [[LEN:%.*]], i32 [[EXTRA:%.*]], i32 [[N:%.*]]) #[[ATTR2:[0-9]+]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[WHILE_COND:%.*]]
+; CHECK:       while.cond:
+; CHECK-NEXT:    [[LEN_ADDR:%.*]] = phi i32 [ [[LEN]], [[ENTRY:%.*]] ], [ [[INC:%.*]], [[WHILE_BODY:%.*]] ]
+; CHECK-NEXT:    [[INC]] = add i32 [[LEN_ADDR]], 1
+; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[INC]], [[N]]
+; CHECK-NEXT:    br i1 [[CMP_NOT]], label [[WHILE_END:%.*]], label [[WHILE_BODY]]
+; CHECK:       while.body:
+; CHECK-NEXT:    [[IDXPROM:%.*]] = zext i32 [[INC]] to i64
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8, ptr [[A]], i64 [[IDXPROM]]
+; CHECK-NEXT:    [[TMP0:%.*]] = load i8, ptr [[ARRAYIDX]], align 1
+; CHECK-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds i8, ptr [[B]], i64 [[IDXPROM]]
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[ARRAYIDX2]], align 1
+; CHECK-NEXT:    [[CMP_NOT2:%.*]] = icmp eq i8 [[TMP0]], [[TMP1]]
+; CHECK-NEXT:    br i1 [[CMP_NOT2]], label [[WHILE_COND]], label [[WHILE_END]]
+; CHECK:       while.end:
+; CHECK-NEXT:    [[INC_LCSSA:%.*]] = phi i32 [ [[INC]], [[WHILE_BODY]] ], [ [[INC]], [[WHILE_COND]] ]
+; CHECK-NEXT:    [[EXTRA_PHI:%.*]] = phi i32 [ [[EXTRA]], [[WHILE_BODY]] ], [ [[EXTRA]], [[WHILE_COND]] ]
+; CHECK-NEXT:    [[RES:%.*]] = add i32 [[INC_LCSSA]], [[EXTRA_PHI]]
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+; LOOP-DEL-LABEL: define i32 @no_implicit_float(
+; LOOP-DEL-SAME: ptr [[A:%.*]], ptr [[B:%.*]], i32 [[LEN:%.*]], i32 [[EXTRA:%.*]], i32 [[N:%.*]]) #[[ATTR2:[0-9]+]] {
+; LOOP-DEL-NEXT:  entry:
+; LOOP-DEL-NEXT:    br label [[WHILE_COND:%.*]]
+; LOOP-DEL:       while.cond:
+; LOOP-DEL-NEXT:    [[LEN_ADDR:%.*]] = phi i32 [ [[LEN]], [[ENTRY:%.*]] ], [ [[INC:%.*]], [[WHILE_BODY:%.*]] ]
+; LOOP-DEL-NEXT:    [[INC]] = add i32 [[LEN_ADDR]], 1
+; LOOP-DEL-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[INC]], [[N]]
+; LOOP-DEL-NEXT:    br i1 [[CMP_NOT]], label [[WHILE_END:%.*]], label [[WHILE_BODY]]
+; LOOP-DEL:       while.body:
+; LOOP-DEL-NEXT:    [[IDXPROM:%.*]] = zext i32 [[INC]] to i64
+; LOOP-DEL-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8, ptr [[A]], i64 [[IDXPROM]]
+; LOOP-DEL-NEXT:    [[TMP0:%.*]] = load i8, ptr [[ARRAYIDX]], align 1
+; LOOP-DEL-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds i8, ptr [[B]], i64 [[IDXPROM]]
+; LOOP-DEL-NEXT:    [[TMP1:%.*]] = load i8, ptr [[ARRAYIDX2]], align 1
+; LOOP-DEL-NEXT:    [[CMP_NOT2:%.*]] = icmp eq i8 [[TMP0]], [[TMP1]]
+; LOOP-DEL-NEXT:    br i1 [[CMP_NOT2]], label [[WHILE_COND]], label [[WHILE_END]]
+; LOOP-DEL:       while.end:
+; LOOP-DEL-NEXT:    [[INC_LCSSA:%.*]] = phi i32 [ [[INC]], [[WHILE_BODY]] ], [ [[INC]], [[WHILE_COND]] ]
+; LOOP-DEL-NEXT:    [[EXTRA_PHI:%.*]] = phi i32 [ [[EXTRA]], [[WHILE_BODY]] ], [ [[EXTRA]], [[WHILE_COND]] ]
+; LOOP-DEL-NEXT:    [[RES:%.*]] = add i32 [[INC_LCSSA]], [[EXTRA_PHI]]
+; LOOP-DEL-NEXT:    ret i32 [[RES]]
+;
+; NO-TRANSFORM-LABEL: define i32 @no_implicit_float(
+; NO-TRANSFORM-SAME: ptr [[A:%.*]], ptr [[B:%.*]], i32 [[LEN:%.*]], i32 [[EXTRA:%.*]], i32 [[N:%.*]]) #[[ATTR1:[0-9]+]] {
+; NO-TRANSFORM-NEXT:  entry:
+; NO-TRANSFORM-NEXT:    br label [[WHILE_COND:%.*]]
+; NO-TRANSFORM:       while.cond:
+; NO-TRANSFORM-NEXT:    [[LEN_ADDR:%.*]] = phi i32 [ [[LEN]], [[ENTRY:%.*]] ], [ [[INC:%.*]], [[WHILE_BODY:%.*]] ]
+; NO-TRANSFORM-NEXT:    [[INC]] = add i32 [[LEN_ADDR]], 1
+; NO-TRANSFORM-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[INC]], [[N]]
+; NO-TRANSFORM-NEXT:    br i1 [[CMP_NOT]], label [[WHILE_END:%.*]], label [[WHILE_BODY]]
+; NO-TRANSFORM:       while.body:
+; NO-TRANSFORM-NEXT:    [[IDXPROM:%.*]] = zext i32 [[INC]] to i64
+; NO-TRANSFORM-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8, ptr [[A]], i64 [[IDXPROM]]
+; NO-TRANSFORM-NEXT:    [[TMP0:%.*]] = load i8, ptr [[ARRAYIDX]], align 1
+; NO-TRANSFORM-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds i8, ptr [[B]], i64 [[IDXPROM]]
+; NO-TRANSFORM-NEXT:    [[TMP1:%.*]] = load i8, ptr [[ARRAYIDX2]], align 1
+; NO-TRANSFORM-NEXT:    [[CMP_NOT2:%.*]] = icmp eq i8 [[TMP0]], [[TMP1]]
+; NO-TRANSFORM-NEXT:    br i1 [[CMP_NOT2]], label [[WHILE_COND]], label [[WHILE_END]]
+; NO-TRANSFORM:       while.end:
+; NO-TRANSFORM-NEXT:    [[INC_LCSSA:%.*]] = phi i32 [ [[INC]], [[WHILE_BODY]] ], [ [[INC]], [[WHILE_COND]] ]
+; NO-TRANSFORM-NEXT:    [[EXTRA_PHI:%.*]] = phi i32 [ [[EXTRA]], [[WHILE_BODY]] ], [ [[EXTRA]], [[WHILE_COND]] ]
+; NO-TRANSFORM-NEXT:    [[RES:%.*]] = add i32 [[INC_LCSSA]], [[EXTRA_PHI]]
+; NO-TRANSFORM-NEXT:    ret i32 [[RES]]
+;
+entry:
+  br label %while.cond
+
+while.cond:
+  %len.addr = phi i32 [ %len, %entry ], [ %inc, %while.body ]
+  %inc = add i32 %len.addr, 1
+  %cmp.not = icmp eq i32 %inc, %n
+  br i1 %cmp.not, label %while.end, label %while.body
+
+while.body:
+  %idxprom = zext i32 %inc to i64
+  %arrayidx = getelementptr inbounds i8, ptr %a, i64 %idxprom
+  %0 = load i8, ptr %arrayidx
+  %arrayidx2 = getelementptr inbounds i8, ptr %b, i64 %idxprom
+  %1 = load i8, ptr %arrayidx2
+  %cmp.not2 = icmp eq i8 %0, %1
+  br i1 %cmp.not2, label %while.cond, label %while.end
+
+while.end:
+  %inc.lcssa = phi i32 [ %inc, %while.body ], [ %inc, %while.cond ]
+  %extra.phi = phi i32 [ %extra, %while.body ], [ %extra, %while.cond ]
+  %res = add i32 %inc.lcssa, %extra.phi
+  ret i32 %res
+}
+