Hexagon loop idiom pass segfaults when -debug present (llvm#121828)

There was an unprotected use of a function that could return the null
pointer.

---------

Co-authored-by: Steve Walk <[email protected]>

Author: swalk-qualcomm

llvm/lib/Target/Hexagon/HexagonLoopIdiomRecognition.cpp

@@ -1796,6 +1796,8 @@ bool PolynomialMultiplyRecognize::recognize() {
     IterCount = CV->getValue()->getZExtValue() + 1;
 
   Value *CIV = getCountIV(LoopB);
+  if (CIV == nullptr)
+    return false;
   ParsedValues PV;
   Simplifier PreSimp;
   PV.IterCount = IterCount;

llvm/test/CodeGen/Hexagon/loopIdiom.ll

@@ -0,0 +1,75 @@
+; RUN: opt -debug -S -march=hexagon -O2  < %s | FileCheck %s
+; REQUIRES: asserts
+; CHECK: define dso_local void @complexMultAccum
+target triple = "hexagon"
+
+; Function Attrs: noinline nounwind
+define dso_local void @complexMultAccum(i32 noundef %n) #0 {
+entry:
+  %n.addr = alloca i32, align 4
+  %run_c_code = alloca i8, align 1
+  %run_asm_code = alloca i8, align 1
+  %iOutter = alloca i32, align 4
+  %iOutter1 = alloca i32, align 4
+  store i32 %n, ptr %n.addr, align 4
+  store i8 1, ptr %run_c_code, align 1
+  store i8 0, ptr %run_asm_code, align 1
+  %0 = load i8, ptr %run_c_code, align 1
+  %tobool = icmp ne i8 %0, 0
+  br i1 %tobool, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  store i32 0, ptr %iOutter, align 4
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc, %if.then
+  %1 = load i32, ptr %iOutter, align 4
+  %cmp = icmp slt i32 %1, 2
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body
+  %2 = load i32, ptr %iOutter, align 4
+  %inc = add nsw i32 %2, 1
+  store i32 %inc, ptr %iOutter, align 4
+  br label %for.cond, !llvm.loop !3
+
+for.end:                                          ; preds = %for.cond
+  store i32 0, ptr %iOutter1, align 4
+  br label %for.cond2
+
+for.cond2:                                        ; preds = %for.inc5, %for.end
+  %3 = load i32, ptr %iOutter1, align 4
+  %cmp3 = icmp slt i32 %3, 2
+  br i1 %cmp3, label %for.body4, label %for.end7
+
+for.body4:                                        ; preds = %for.cond2
+  br label %for.inc5
+
+for.inc5:                                         ; preds = %for.body4
+  %4 = load i32, ptr %iOutter1, align 4
+  %inc6 = add nsw i32 %4, 1
+  store i32 %inc6, ptr %iOutter1, align 4
+  br label %for.cond2, !llvm.loop !5
+
+for.end7:                                         ; preds = %for.cond2
+  br label %if.end
+
+if.end:                                           ; preds = %for.end7, %entry
+  ret void
+}
+
+attributes #0 = { noinline nounwind "approx-func-fp-math"="true" "frame-pointer"="all" "no-infs-fp-math"="true" "no-nans-fp-math"="true" "no-signed-zeros-fp-math"="true" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="hexagonv79" "target-features"="+v79,-long-calls" "unsafe-fp-math"="true" }
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 7, !"frame-pointer", i32 2}
+!2 = !{!"LLVM Clang"}
+!3 = distinct !{!3, !4}
+!4 = !{!"llvm.loop.mustprogress"}
+!5 = distinct !{!5, !4}
+