[llvm] Reland "RegisterCoalescer: Add implicit-def of super register when coalescing SUBREG_TO_REG" (PR #123632)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,125 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s | FileCheck %s
+
+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"
+target triple = "x86_64-unknown-linux-gnu"
+
+;
+; Reproducer from https://github.com/llvm/llvm-project/issues/76416
+;
+
+ at load_p = external global ptr, align 8
+ at load_data = external global i8, align 1
+
+define dso_local void @pr76416() {
+; CHECK-LABEL: pr76416:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    movl $0, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT:    cmpl $3, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT:    jg .LBB0_3
+; CHECK-NEXT:    .p2align 4
+; CHECK-NEXT:  .LBB0_2: # %for.body
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    incl -{{[0-9]+}}(%rsp)
+; CHECK-NEXT:    cmpl $3, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT:    jle .LBB0_2
+; CHECK-NEXT:  .LBB0_3: # %for.end
+; CHECK-NEXT:    movl $0, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT:    movq load_p at GOTPCREL(%rip), %rax
+; CHECK-NEXT:    movq load_data at GOTPCREL(%rip), %rcx
+; CHECK-NEXT:    .p2align 4
+; CHECK-NEXT:  .LBB0_4: # %for.cond1
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    movq (%rax), %rdx
+; CHECK-NEXT:    movslq -{{[0-9]+}}(%rsp), %rsi
+; CHECK-NEXT:    movzbl (%rdx,%rsi), %edx
+; CHECK-NEXT:    movb %dl, (%rcx)
+; CHECK-NEXT:    leal 1(%rsi), %edx
+; CHECK-NEXT:    movl %edx, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT:    jmp .LBB0_4
+entry:
+  %i = alloca i32, align 4
+  store i32 0, ptr %i, align 4
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %0 = load i32, ptr %i, align 4
+  %cmp = icmp slt i32 %0, 4
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  call void asm sideeffect "", "{ax},~{dirflag},~{fpsr},~{flags}"(i8 0) nounwind
+  %1 = load i32, ptr %i, align 4
+  %inc = add nsw i32 %1, 1
+  store i32 %inc, ptr %i, align 4
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  store i32 0, ptr %i, align 4
+  br label %for.cond1
+
+for.cond1:                                        ; preds = %for.cond1, %for.end
+  call void asm sideeffect "", "N{dx},~{dirflag},~{fpsr},~{flags}"(i32 poison) nounwind
+  %2 = load ptr, ptr @load_p, align 8
+  %regs = getelementptr inbounds { [4 x i8] }, ptr %2, i32 0, i32 0
+  %3 = load i32, ptr %i, align 4
+  %idxprom = sext i32 %3 to i64
+  %arrayidx = getelementptr inbounds [4 x i8], ptr %regs, i64 0, i64 %idxprom
+  %4 = load i8, ptr %arrayidx, align 1
+  store i8 %4, ptr @load_data, align 1
+  %5 = load i32, ptr %i, align 4
+  %inc5 = add nsw i32 %5, 1
+  store i32 %inc5, ptr %i, align 4
+  br label %for.cond1
+}
+
+;
+; Related reproducer as reported on https://github.com/llvm/llvm-project/commit/0e46b49de43349f8cbb2a7d4c6badef6d16e31ae#commitcomment-136147998
+;
+
+define void @f(i1 %cmp.not.i.i.i) {
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arsenm wrote:

I think this one is the same as  llvm/test/CodeGen/X86/coalescer-add-implicit-def-subreg-to-reg-regression.ll

https://github.com/llvm/llvm-project/pull/123632