[PATCH] D88548: Fix limit behavior of dynamic alloca

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When the allocation size is 0, we shouldn't probe. Within [1,  PAGE_SIZE], we should probe once etc.

      

This fixes https://bugs.llvm.org/show_bug.cgi?id=47657


https://reviews.llvm.org/D88548

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/stack-clash-dynamic-alloca.ll


Index: llvm/test/CodeGen/X86/stack-clash-dynamic-alloca.ll
===================================================================
--- llvm/test/CodeGen/X86/stack-clash-dynamic-alloca.ll
+++ llvm/test/CodeGen/X86/stack-clash-dynamic-alloca.ll
@@ -24,12 +24,12 @@
 ; CHECK-X86-64-NEXT:  	andq	$-16, %rcx
 ; CHECK-X86-64-NEXT:  	subq	%rcx, %rax
 ; CHECK-X86-64-NEXT:  	cmpq	%rsp, %rax
-; CHECK-X86-64-NEXT:  	jl	.LBB0_3
+; CHECK-X86-64-NEXT:  	jle	.LBB0_3
 ; CHECK-X86-64-NEXT:  .LBB0_2: # =>This Inner Loop Header: Depth=1
 ; CHECK-X86-64-NEXT:  	movq	$0, (%rsp)
 ; CHECK-X86-64-NEXT:  	subq	$4096, %rsp # imm = 0x1000
 ; CHECK-X86-64-NEXT:  	cmpq	%rsp, %rax
-; CHECK-X86-64-NEXT:  	jge	.LBB0_2
+; CHECK-X86-64-NEXT:  	jg	.LBB0_2
 ; CHECK-X86-64-NEXT:  .LBB0_3:
 ; CHECK-X86-64-NEXT:  	movq	%rax, %rsp
 ; CHECK-X86-64-NEXT:  	movl	$1, 4792(%rax)
@@ -54,12 +54,12 @@
 ; CHECK-X86-32-NEXT:    andl    $-16, %ecx
 ; CHECK-X86-32-NEXT:    subl    %ecx, %eax
 ; CHECK-X86-32-NEXT:    cmpl    %esp, %eax
-; CHECK-X86-32-NEXT:    jl  .LBB0_3
+; CHECK-X86-32-NEXT:    jle  .LBB0_3
 ; CHECK-X86-32-NEXT:  .LBB0_2: # =>This Inner Loop Header: Depth=1
 ; CHECK-X86-32-NEXT:    movl    $0, (%esp)
 ; CHECK-X86-32-NEXT:    subl    $4096, %esp # imm = 0x1000
 ; CHECK-X86-32-NEXT:    cmpl    %esp, %eax
-; CHECK-X86-32-NEXT:    jge .LBB0_2
+; CHECK-X86-32-NEXT:    jg .LBB0_2
 ; CHECK-X86-32-NEXT:  .LBB0_3:
 ; CHECK-X86-32-NEXT:    movl    %eax, %esp
 ; CHECK-X86-32-NEXT:    movl    $1, 4792(%eax)
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -32215,7 +32215,7 @@
 
   BuildMI(testMBB, DL, TII->get(X86::JCC_1))
       .addMBB(tailMBB)
-      .addImm(X86::COND_L);
+      .addImm(X86::COND_LE);
   testMBB->addSuccessor(blockMBB);
   testMBB->addSuccessor(tailMBB);
 


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