wrong code at -O1 and above on x86_64-linux-gnu

[zhendongsu]

This appears to be a recent regression as it doesn't reproduce with 18.1.0 and earlier.

Compiler Explorer: https://godbolt.org/z/T9b4a7z3v

% clangtk -v
clang version 19.0.0git (https://github.com/llvm/llvm-project.git 338cbfef03e0ab58d7b52f3301928c58b194a1b4)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /local/suz-local/software/local/clang-trunk/bin
Build config: +assertions
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Candidate multilib: .;@m64
Selected multilib: .;@m64
% 
% clangtk -O0 small.c; ./a.out
% clangtk -O1 small.c
% ./a.out
Aborted
% cat small.c
int a;
char b(char c, char d) { return c - d; }
int main() {
  int e;
  for (a = -10; a > -11; a--)
    e = b(a, -1);
  if (e > -2)
    __builtin_abort();
  return 0;
}

[dtcxzyw]

Reproducer: https://alive2.llvm.org/ce/z/_3cyuT

target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"

define i1 @src() {
entry:
  br label %for.body

for.body:
  %storemerge4 = phi i32 [ -10, %entry ], [ %dec, %for.body ]
  %dec = add nsw i32 %storemerge4, -1
  %cmp = icmp ugt i32 %dec, -11
  br i1 %cmp, label %for.body, label %for.end

for.end:
  %sub.i.le = shl nsw i32 %storemerge4, 24
  %cmp2 = icmp ugt i32 %sub.i.le, -50331648
  ret i1 %cmp2
}

define i1 @tgt() {
entry:
  br label %for.body

for.body:
  %storemerge4 = phi i32 [ -10, %entry ], [ %dec, %for.body ]
  %dec = add nsw i32 %storemerge4, -1
  %cmp = icmp ugt i32 %dec, -11
  br i1 %cmp, label %for.body, label %for.end

for.end:
  %0 = trunc nuw i32 %storemerge4 to i8
  %cmp2 = icmp ugt i8 %0, -3
  ret i1 %cmp2
}

nuw flag is incorrectly added.

[dtcxzyw]

Caused by 5c7c1f6.