[llvm] [SDAG] Don't allow implicit trunc in getConstant() (PR #117558)

[Nathan Chancellor via llvm-commits]

nathanchance wrote:

@nikic Whoops, looks like the original file got too reduced, how about this one? It reproduces for me at f67ba5855278401728413431216dda5d370ac2e0.

```c
int *get_next_block_base;
char get_next_block_length_0;
void __attribute__get_next_block() {
  int i;
  short temp[20];
  for (i = 0; get_next_block_length_0; i++)
    get_next_block_base[i] += temp[i];
}
```

```llvm
target datalayout = "E-m:e-p:32:32-Fn32-i64:64-n32"
target triple = "powerpc-unknown-linux-gnu"

define void @__attribute__get_next_block() {
entry:
  %temp = alloca [20 x i16], i32 0, align 2
  br label %for.body

for.body:                                         ; preds = %for.body, %entry
  %i.04 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
  %arrayidx = getelementptr [20 x i16], ptr %temp, i32 0, i32 %i.04
  %0 = load i16, ptr %arrayidx, align 2
  %conv = sext i16 %0 to i32
  store i32 %conv, ptr null, align 4
  %inc = add i32 %i.04, 1
  br label %for.body
}
```

```
$ clang --target=powerpc-linux-gnu -O2 -c -o /dev/null decompress_bunzip2.i
clang: llvm/include/llvm/ADT/APInt.h:128: llvm::APInt::APInt(unsigned int, uint64_t, bool, bool): Assertion `llvm::isUIntN(BitWidth, val) && "Value is not an N-bit unsigned value"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: clang --target=powerpc-linux-gnu -O2 -c -o /dev/null decompress_bunzip2.i
1.      <eof> parser at end of file
2.      Code generation
3.      Running pass 'Function Pass Manager' on module 'decompress_bunzip2.i'.
4.      Running pass 'PowerPC DAG->DAG Pattern Instruction Selection' on function '@__attribute__get_next_block'
...

$ llc reduced.ll
llc: llvm/include/llvm/ADT/APInt.h:128: llvm::APInt::APInt(unsigned int, uint64_t, bool, bool): Assertion `llvm::isUIntN(BitWidth, val) && "Value is not an N-bit unsigned value"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: llc reduced.ll
1.      Running pass 'Function Pass Manager' on module 'reduced.ll'.
2.      Running pass 'PowerPC DAG->DAG Pattern Instruction Selection' on function '@__attribute__get_next_block'
 #0 0x000055dde1e70ac8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x5683ac8)
 #1 0x000055dde1e6e57e llvm::sys::RunSignalHandlers() (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x568157e)
 #2 0x000055dde1e71178 SignalHandler(int) Signals.cpp:0:0
 #3 0x00007f88e8ed31d0 (/usr/lib/libc.so.6+0x3d1d0)
 #4 0x00007f88e8f2c3f4 (/usr/lib/libc.so.6+0x963f4)
 #5 0x00007f88e8ed3120 raise (/usr/lib/libc.so.6+0x3d120)
 #6 0x00007f88e8eba4c3 abort (/usr/lib/libc.so.6+0x244c3)
 #7 0x00007f88e8eba3df (/usr/lib/libc.so.6+0x243df)
 #8 0x00007f88e8ecb177 (/usr/lib/libc.so.6+0x35177)
 #9 0x000055dde1c033c8 (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x54163c8)
#10 0x000055dde01f7ab4 (anonymous namespace)::PPCDAGToDAGISel::selectFrameIndex(llvm::SDNode*, llvm::SDNode*, unsigned long) PPCISelDAGToDAG.cpp:0:0
#11 0x000055dde01eb27c (anonymous namespace)::PPCDAGToDAGISel::Select(llvm::SDNode*) PPCISelDAGToDAG.cpp:0:0
#12 0x000055dde1c69caf llvm::SelectionDAGISel::DoInstructionSelection() (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x547ccaf)
#13 0x000055dde1c68c38 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x547bc38)
#14 0x000055dde1c66bef llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x5479bef)
#15 0x000055dde1c63a30 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x5476a30)
#16 0x000055dde01e595e (anonymous namespace)::PPCDAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) PPCISelDAGToDAG.cpp:0:0
#17 0x000055dde1c61316 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x5474316)
#18 0x000055dde0f06707 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x4719707)
#19 0x000055dde143c95a llvm::FPPassManager::runOnFunction(llvm::Function&) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x4c4f95a)
#20 0x000055dde1444df2 llvm::FPPassManager::runOnModule(llvm::Module&) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x4c57df2)
#21 0x000055dde143d426 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x4c50426)
#22 0x000055dddf89af0e compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#23 0x000055dddf89879d main (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x30ab79d)
#24 0x00007f88e8ebbe08 (/usr/lib/libc.so.6+0x25e08)
#25 0x00007f88e8ebbecc __libc_start_main (/usr/lib/libc.so.6+0x25ecc)
#26 0x000055dddf8945e5 _start (/mnt/nvme/tmp/cvise.kJkUnw63jz/install/llvm-main/bin/llc+0x30a75e5)
```

https://github.com/llvm/llvm-project/pull/117558