[llvm] [CGP] Do not fold ret value if constant in `dupRetToEnableTailCallOpts` (PR #76613)
via llvm-commits
llvm-commits at lists.llvm.org
Sat Dec 30 03:38:52 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-debuginfo
@llvm/pr-subscribers-backend-x86
Author: Antonio Frighetto (antoniofrighetto)
<details>
<summary>Changes</summary>
Unless the returned value is a constant, which may result in duplicated code later in codegen, there should be no reason not to refrain from further tail call optimization opportunities. Consider also the cases in which incoming values in phi-nodes, not coming directly from call instructions, may still be folded.
Fixes: https://github.com/llvm/llvm-project/issues/75455.
---
Full diff: https://github.com/llvm/llvm-project/pull/76613.diff
6 Files Affected:
- (modified) llvm/lib/CodeGen/CodeGenPrepare.cpp (+10-2)
- (modified) llvm/test/CodeGen/Thumb2/constant-islands-cbz.ll (+8-10)
- (modified) llvm/test/CodeGen/X86/tail-dup-merge-loop-headers.ll (+63-66)
- (modified) llvm/test/CodeGen/X86/tailcall-cgp-dup.ll (+51)
- (modified) llvm/test/CodeGen/X86/x86-shrink-wrapping.ll (+2-2)
- (modified) llvm/test/DebugInfo/X86/live-debug-values-expr-conflict.ll (+8-8)
``````````diff
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 6e99fb133e26a9..8c28333ac532d9 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -2532,7 +2532,8 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB,
}
PN = dyn_cast<PHINode>(V);
- if (!PN)
+
+ if (isa<Constant>(V))
return false;
}
@@ -2569,8 +2570,15 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB,
Value *IncomingVal = PN->getIncomingValue(I)->stripPointerCasts();
CallInst *CI = dyn_cast<CallInst>(IncomingVal);
BasicBlock *PredBB = PN->getIncomingBlock(I);
+ // Do we have a call whose return value may have been optimized out (e.g.
+ // __builtin_memset) and an unconditional jump as terminator eligible to
+ // be folded?
+ if (!CI && PredBB && PredBB->getSingleSuccessor() == BB)
+ CI = dyn_cast_or_null<CallInst>(
+ PredBB->getTerminator()->getPrevNonDebugInstruction(true));
+
// Make sure the phi value is indeed produced by the tail call.
- if (CI && CI->hasOneUse() && CI->getParent() == PredBB &&
+ if (CI && CI->getParent() == PredBB && CI->getNumUses() <= 1 &&
TLI->mayBeEmittedAsTailCall(CI) &&
attributesPermitTailCall(F, CI, RetI, *TLI))
TailCallBBs.push_back(PredBB);
diff --git a/llvm/test/CodeGen/Thumb2/constant-islands-cbz.ll b/llvm/test/CodeGen/Thumb2/constant-islands-cbz.ll
index fc42d4e0e4d8c0..6e5cf4d335d94e 100644
--- a/llvm/test/CodeGen/Thumb2/constant-islands-cbz.ll
+++ b/llvm/test/CodeGen/Thumb2/constant-islands-cbz.ll
@@ -8,12 +8,11 @@ define ptr @test(ptr returned %this, i32 %event_size, ptr %event_pointer) {
; CHECK-T1-NEXT: .save {r4, lr}
; CHECK-T1-NEXT: push {r4, lr}
; CHECK-T1-NEXT: mov r4, r0
-; CHECK-T1-NEXT: movs r0, #0
-; CHECK-T1-NEXT: str r0, [r4, #4]
-; CHECK-T1-NEXT: str r0, [r4, #8]
-; CHECK-T1-NEXT: str r0, [r4, #12]
-; CHECK-T1-NEXT: str r0, [r4, #16]
-; CHECK-T1-NEXT: mov r0, r4
+; CHECK-T1-NEXT: movs r3, #0
+; CHECK-T1-NEXT: str r3, [r0, #4]
+; CHECK-T1-NEXT: str r3, [r0, #8]
+; CHECK-T1-NEXT: str r3, [r0, #12]
+; CHECK-T1-NEXT: str r3, [r0, #16]
; CHECK-T1-NEXT: cbz r2, .LBB0_2
; CHECK-T1-NEXT: @ %bb.1: @ %if.else
; CHECK-T1-NEXT: bl equeue_create_inplace
@@ -28,11 +27,10 @@ define ptr @test(ptr returned %this, i32 %event_size, ptr %event_pointer) {
; CHECK-T2: @ %bb.0: @ %entry
; CHECK-T2-NEXT: .save {r4, lr}
; CHECK-T2-NEXT: push {r4, lr}
+; CHECK-T2-NEXT: movs r3, #0
; CHECK-T2-NEXT: mov r4, r0
-; CHECK-T2-NEXT: movs r0, #0
-; CHECK-T2-NEXT: strd r0, r0, [r4, #4]
-; CHECK-T2-NEXT: strd r0, r0, [r4, #12]
-; CHECK-T2-NEXT: mov r0, r4
+; CHECK-T2-NEXT: strd r3, r3, [r0, #4]
+; CHECK-T2-NEXT: strd r3, r3, [r0, #12]
; CHECK-T2-NEXT: cbz r2, .LBB0_2
; CHECK-T2-NEXT: @ %bb.1: @ %if.else
; CHECK-T2-NEXT: bl equeue_create_inplace
diff --git a/llvm/test/CodeGen/X86/tail-dup-merge-loop-headers.ll b/llvm/test/CodeGen/X86/tail-dup-merge-loop-headers.ll
index 937cc173e7faef..404b8b13328de7 100644
--- a/llvm/test/CodeGen/X86/tail-dup-merge-loop-headers.ll
+++ b/llvm/test/CodeGen/X86/tail-dup-merge-loop-headers.ll
@@ -95,102 +95,92 @@ define i32 @loop_shared_header(i8* %exe, i32 %exesz, i32 %headsize, i32 %min, i3
; CHECK-NEXT: pushq %r12
; CHECK-NEXT: pushq %rbx
; CHECK-NEXT: pushq %rax
-; CHECK-NEXT: movl $1, %ebx
; CHECK-NEXT: xorl %eax, %eax
; CHECK-NEXT: testb %al, %al
-; CHECK-NEXT: jne .LBB1_24
+; CHECK-NEXT: jne .LBB1_22
; CHECK-NEXT: # %bb.1: # %if.end19
; CHECK-NEXT: movl %esi, %ebp
-; CHECK-NEXT: movq %rdi, %r15
-; CHECK-NEXT: movl (%rax), %r13d
-; CHECK-NEXT: leal (,%r13,4), %ebx
-; CHECK-NEXT: movl %ebx, %r12d
+; CHECK-NEXT: movq %rdi, %r14
+; CHECK-NEXT: movl (%rax), %r12d
+; CHECK-NEXT: leal (,%r12,4), %r13d
+; CHECK-NEXT: movl %r13d, %r15d
; CHECK-NEXT: movl $1, %esi
-; CHECK-NEXT: movq %r12, %rdi
+; CHECK-NEXT: movq %r15, %rdi
; CHECK-NEXT: callq cli_calloc at PLT
; CHECK-NEXT: testl %ebp, %ebp
-; CHECK-NEXT: je .LBB1_23
+; CHECK-NEXT: je .LBB1_22
; CHECK-NEXT: # %bb.2: # %if.end19
-; CHECK-NEXT: testl %r13d, %r13d
-; CHECK-NEXT: je .LBB1_23
+; CHECK-NEXT: testl %r12d, %r12d
+; CHECK-NEXT: je .LBB1_22
; CHECK-NEXT: # %bb.3: # %if.end19
-; CHECK-NEXT: movq %rax, %r14
+; CHECK-NEXT: movq %rax, %rbx
; CHECK-NEXT: xorl %eax, %eax
; CHECK-NEXT: testb %al, %al
-; CHECK-NEXT: jne .LBB1_23
+; CHECK-NEXT: jne .LBB1_22
; CHECK-NEXT: # %bb.4: # %if.end19
-; CHECK-NEXT: cmpq %r15, %r14
-; CHECK-NEXT: jb .LBB1_23
+; CHECK-NEXT: cmpq %r14, %rbx
+; CHECK-NEXT: jb .LBB1_22
; CHECK-NEXT: # %bb.5: # %if.end50
-; CHECK-NEXT: movq %r14, %rdi
-; CHECK-NEXT: movq %r12, %rdx
+; CHECK-NEXT: movq %rbx, %rdi
+; CHECK-NEXT: movq %r15, %rdx
; CHECK-NEXT: callq memcpy at PLT
-; CHECK-NEXT: cmpl $4, %ebx
-; CHECK-NEXT: jb .LBB1_26
+; CHECK-NEXT: cmpl $4, %r13d
+; CHECK-NEXT: jb .LBB1_21
; CHECK-NEXT: # %bb.6: # %shared_preheader
; CHECK-NEXT: movb $32, %cl
; CHECK-NEXT: xorl %eax, %eax
-; CHECK-NEXT: jmp .LBB1_8
+; CHECK-NEXT: jmp .LBB1_7
; CHECK-NEXT: .p2align 4, 0x90
-; CHECK-NEXT: .LBB1_7: # %merge_predecessor_split
-; CHECK-NEXT: # in Loop: Header=BB1_8 Depth=1
+; CHECK-NEXT: .LBB1_17: # %merge_predecessor_split
+; CHECK-NEXT: # in Loop: Header=BB1_7 Depth=1
; CHECK-NEXT: movb $32, %cl
-; CHECK-NEXT: .LBB1_8: # %outer_loop_header
+; CHECK-NEXT: .LBB1_7: # %outer_loop_header
; CHECK-NEXT: # =>This Loop Header: Depth=1
-; CHECK-NEXT: # Child Loop BB1_9 Depth 2
-; CHECK-NEXT: testl %r13d, %r13d
-; CHECK-NEXT: je .LBB1_16
+; CHECK-NEXT: # Child Loop BB1_11 Depth 2
+; CHECK-NEXT: testl %r12d, %r12d
+; CHECK-NEXT: je .LBB1_8
; CHECK-NEXT: .p2align 4, 0x90
-; CHECK-NEXT: .LBB1_9: # %shared_loop_header
-; CHECK-NEXT: # Parent Loop BB1_8 Depth=1
+; CHECK-NEXT: .LBB1_11: # %shared_loop_header
+; CHECK-NEXT: # Parent Loop BB1_7 Depth=1
; CHECK-NEXT: # => This Inner Loop Header: Depth=2
-; CHECK-NEXT: testq %r14, %r14
-; CHECK-NEXT: jne .LBB1_25
-; CHECK-NEXT: # %bb.10: # %inner_loop_body
-; CHECK-NEXT: # in Loop: Header=BB1_9 Depth=2
+; CHECK-NEXT: testq %rbx, %rbx
+; CHECK-NEXT: jne .LBB1_20
+; CHECK-NEXT: # %bb.12: # %inner_loop_body
+; CHECK-NEXT: # in Loop: Header=BB1_11 Depth=2
; CHECK-NEXT: testb %al, %al
-; CHECK-NEXT: je .LBB1_9
-; CHECK-NEXT: # %bb.11: # %if.end96.i
-; CHECK-NEXT: # in Loop: Header=BB1_8 Depth=1
-; CHECK-NEXT: cmpl $3, %r13d
-; CHECK-NEXT: jae .LBB1_20
-; CHECK-NEXT: # %bb.12: # %if.end287.i
-; CHECK-NEXT: # in Loop: Header=BB1_8 Depth=1
+; CHECK-NEXT: je .LBB1_11
+; CHECK-NEXT: # %bb.13: # %if.end96.i
+; CHECK-NEXT: # in Loop: Header=BB1_7 Depth=1
+; CHECK-NEXT: cmpl $3, %r12d
+; CHECK-NEXT: jae .LBB1_14
+; CHECK-NEXT: # %bb.15: # %if.end287.i
+; CHECK-NEXT: # in Loop: Header=BB1_7 Depth=1
; CHECK-NEXT: testb %al, %al
; CHECK-NEXT: # implicit-def: $cl
-; CHECK-NEXT: jne .LBB1_8
-; CHECK-NEXT: # %bb.13: # %if.end308.i
-; CHECK-NEXT: # in Loop: Header=BB1_8 Depth=1
+; CHECK-NEXT: jne .LBB1_7
+; CHECK-NEXT: # %bb.16: # %if.end308.i
+; CHECK-NEXT: # in Loop: Header=BB1_7 Depth=1
; CHECK-NEXT: testb %al, %al
-; CHECK-NEXT: je .LBB1_7
-; CHECK-NEXT: # %bb.14: # %if.end335.i
-; CHECK-NEXT: # in Loop: Header=BB1_8 Depth=1
+; CHECK-NEXT: je .LBB1_17
+; CHECK-NEXT: # %bb.18: # %if.end335.i
+; CHECK-NEXT: # in Loop: Header=BB1_7 Depth=1
; CHECK-NEXT: xorl %ecx, %ecx
; CHECK-NEXT: testb %cl, %cl
-; CHECK-NEXT: jne .LBB1_8
-; CHECK-NEXT: # %bb.15: # %merge_other
-; CHECK-NEXT: # in Loop: Header=BB1_8 Depth=1
+; CHECK-NEXT: jne .LBB1_7
+; CHECK-NEXT: # %bb.19: # %merge_other
+; CHECK-NEXT: # in Loop: Header=BB1_7 Depth=1
; CHECK-NEXT: # implicit-def: $cl
-; CHECK-NEXT: jmp .LBB1_8
-; CHECK-NEXT: .LBB1_23:
-; CHECK-NEXT: movl $1, %ebx
-; CHECK-NEXT: jmp .LBB1_24
-; CHECK-NEXT: .LBB1_16: # %while.cond.us1412.i
+; CHECK-NEXT: jmp .LBB1_7
+; CHECK-NEXT: .LBB1_8: # %while.cond.us1412.i
; CHECK-NEXT: xorl %eax, %eax
; CHECK-NEXT: testb %al, %al
-; CHECK-NEXT: movl $1, %ebx
-; CHECK-NEXT: jne .LBB1_18
-; CHECK-NEXT: # %bb.17: # %while.cond.us1412.i
+; CHECK-NEXT: jne .LBB1_10
+; CHECK-NEXT: # %bb.9: # %while.cond.us1412.i
; CHECK-NEXT: decb %cl
-; CHECK-NEXT: jne .LBB1_24
-; CHECK-NEXT: .LBB1_18: # %if.end41.us1436.i
-; CHECK-NEXT: .LBB1_20: # %if.then99.i
-; CHECK-NEXT: movq .str.6 at GOTPCREL(%rip), %rdi
-; CHECK-NEXT: xorl %ebx, %ebx
-; CHECK-NEXT: xorl %eax, %eax
-; CHECK-NEXT: callq cli_dbgmsg at PLT
-; CHECK-NEXT: .LBB1_24: # %cleanup
-; CHECK-NEXT: movl %ebx, %eax
+; CHECK-NEXT: je .LBB1_10
+; CHECK-NEXT: .LBB1_22: # %cleanup
+; CHECK-NEXT: movl $1, %eax
+; CHECK-NEXT: .LBB1_23: # %cleanup
; CHECK-NEXT: addq $8, %rsp
; CHECK-NEXT: popq %rbx
; CHECK-NEXT: popq %r12
@@ -199,8 +189,15 @@ define i32 @loop_shared_header(i8* %exe, i32 %exesz, i32 %headsize, i32 %min, i3
; CHECK-NEXT: popq %r15
; CHECK-NEXT: popq %rbp
; CHECK-NEXT: retq
-; CHECK-NEXT: .LBB1_25: # %wunpsect.exit.thread.loopexit389
-; CHECK-NEXT: .LBB1_26: # %wunpsect.exit.thread.loopexit391
+; CHECK-NEXT: .LBB1_14: # %if.then99.i
+; CHECK-NEXT: movq .str.6 at GOTPCREL(%rip), %rdi
+; CHECK-NEXT: xorl %eax, %eax
+; CHECK-NEXT: callq cli_dbgmsg at PLT
+; CHECK-NEXT: xorl %eax, %eax
+; CHECK-NEXT: jmp .LBB1_23
+; CHECK-NEXT: .LBB1_20: # %wunpsect.exit.thread.loopexit389
+; CHECK-NEXT: .LBB1_10: # %if.end41.us1436.i
+; CHECK-NEXT: .LBB1_21: # %wunpsect.exit.thread.loopexit391
entry:
%0 = load i32, i32* undef, align 4
%mul = shl nsw i32 %0, 2
diff --git a/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll b/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
index 48440558283d45..a52bd0b305bd3f 100644
--- a/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
+++ b/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
@@ -184,3 +184,54 @@ return:
%retval = phi ptr [ %ptr, %if.then ], [ %obj, %entry ]
ret ptr %retval
}
+
+define noundef ptr @memset_tailc(ptr noundef %0, i64 noundef %1) {
+; CHECK-LABEL: memset_tailc:
+; CHECK: ## %bb.0:
+; CHECK-NEXT: testq %rdi, %rdi
+; CHECK-NEXT: je LBB4_1
+; CHECK-NEXT: ## %bb.2:
+; CHECK-NEXT: movq %rsi, %rdx
+; CHECK-NEXT: xorl %esi, %esi
+; CHECK-NEXT: jmp _memset ## TAILCALL
+; CHECK-NEXT: LBB4_1:
+; CHECK-NEXT: movq %rdi, %rax
+; CHECK-NEXT: retq
+ %3 = icmp eq ptr %0, null
+ br i1 %3, label %5, label %4
+
+4:
+ tail call void @llvm.memset.p0.i64(ptr nonnull align 1 %0, i8 0, i64 %1, i1 false)
+ br label %5
+
+5:
+ ret ptr %0
+}
+
+define noundef ptr @memcpy_tailc(ptr noundef %0, i64 noundef %1, ptr noundef %2) {
+; CHECK-LABEL: memcpy_tailc:
+; CHECK: ## %bb.0:
+; CHECK-NEXT: testq %rsi, %rsi
+; CHECK-NEXT: je LBB5_1
+; CHECK-NEXT: ## %bb.2:
+; CHECK-NEXT: movq %rsi, %rax
+; CHECK-NEXT: movq %rdx, %rsi
+; CHECK-NEXT: movq %rax, %rdx
+; CHECK-NEXT: jmp _memcpy ## TAILCALL
+; CHECK-NEXT: LBB5_1:
+; CHECK-NEXT: movq %rdx, %rax
+; CHECK-NEXT: retq
+ %4 = icmp eq i64 %1, 0
+ br i1 %4, label %6, label %5
+
+5:
+ tail call void @llvm.memcpy.p0.p0.i64(ptr align 1 %0, ptr align 1 %2, i64 %1, i1 false)
+ br label %6
+
+6:
+ %7 = phi ptr [ %0, %5 ], [ %2, %3 ]
+ ret ptr %7
+}
+
+declare void @llvm.memcpy.p0.p0.i64(ptr noalias nocapture writeonly, ptr noalias nocapture readonly, i64, i1 immarg) #1
+declare void @llvm.memset.p0.i64(ptr nocapture writeonly, i8, i64, i1 immarg)
diff --git a/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll b/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll
index fab3847b3a2c51..eb2e00fb90429c 100644
--- a/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll
+++ b/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll
@@ -477,8 +477,8 @@ define i32 @inlineAsm(i32 %cond, i32 %N) {
; ENABLE-NEXT: popq %rbx
; ENABLE-NEXT: retq
; ENABLE-NEXT: LBB6_4: ## %if.else
+; ENABLE-NEXT: addl %esi, %esi
; ENABLE-NEXT: movl %esi, %eax
-; ENABLE-NEXT: addl %esi, %eax
; ENABLE-NEXT: retq
;
; DISABLE-LABEL: inlineAsm:
@@ -509,8 +509,8 @@ define i32 @inlineAsm(i32 %cond, i32 %N) {
; DISABLE-NEXT: popq %rbx
; DISABLE-NEXT: retq
; DISABLE-NEXT: LBB6_4: ## %if.else
+; DISABLE-NEXT: addl %esi, %esi
; DISABLE-NEXT: movl %esi, %eax
-; DISABLE-NEXT: addl %esi, %eax
; DISABLE-NEXT: popq %rbx
; DISABLE-NEXT: retq
entry:
diff --git a/llvm/test/DebugInfo/X86/live-debug-values-expr-conflict.ll b/llvm/test/DebugInfo/X86/live-debug-values-expr-conflict.ll
index afce27ee4abb9b..2769d39fa54aa2 100644
--- a/llvm/test/DebugInfo/X86/live-debug-values-expr-conflict.ll
+++ b/llvm/test/DebugInfo/X86/live-debug-values-expr-conflict.ll
@@ -24,18 +24,18 @@
; one in the block two, and none in block three.
; CHECK: ![[BAZVAR:[0-9]+]] = !DILocalVariable(name: "baz",
; CHECK-LABEL: bb.0.entry:
-; CHECK: DBG_VALUE {{[0-9a-zA-Z$%_]*}}, $noreg, ![[BAZVAR]],
+; CHECK: DBG_VALUE {{[0-9a-zA-Z$%_]*}}, $noreg, ![[BAZVAR]],
; CHECK-SAME: !DIExpression()
; CHECK-LABEL: bb.1.if.then:
-; CHECK-LABEL: bb.2.if.else:
-; CHECK: DBG_VALUE {{[0-9a-zA-Z$%_]*}}, $noreg, ![[BAZVAR]],
+; CHECK-LABEL: bb.3.if.else:
+; CHECK: DBG_VALUE {{[0-9a-zA-Z$%_]*}}, $noreg, ![[BAZVAR]],
; CHECK-SAME: !DIExpression()
-; CHECK: DBG_VALUE_LIST ![[BAZVAR]],
-; CHECK-SAME: !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_plus_uconst, 1, DW_OP_stack_value)
-; CHECK-SAME: {{[0-9a-zA-Z$%_]*}}
-; CHECK-LABEL: bb.3.if.end:
+; CHECK: DBG_VALUE_LIST ![[BAZVAR]],
+; CHECK-SAME: !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_plus_uconst, 1, DW_OP_stack_value)
+; CHECK-SAME: {{[0-9a-zA-Z$%_]*}}
+; CHECK-LABEL: bb.2.if.then:
; CHECK-NOT: DBG_VALUE
-; CHECK-NOT: DBG_VALUE_LIST
+; CHECK-NOT: DBG_VALUE_LIST
declare void @escape1(i32)
declare void @escape2(i32)
``````````
</details>
https://github.com/llvm/llvm-project/pull/76613
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