[libc][i386] setjmp/longjmp (llvm#112437)

Link: llvm#93709

Author: nickdesaulniers

libc/include/llvm-libc-types/jmp_buf.h

@@ -19,6 +19,13 @@ typedef struct {
   __UINT64_TYPE__ r15;
   __UINTPTR_TYPE__ rsp;
   __UINTPTR_TYPE__ rip;
+#elif defined(__i386__)
+  long ebx;
+  long esi;
+  long edi;
+  long ebp;
+  long esp;
+  long eip;
 #elif defined(__riscv)
   /* Program counter.  */
   long int __pc;

libc/src/setjmp/x86_64/longjmp.cpp

@@ -11,12 +11,34 @@
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 
-#if !defined(LIBC_TARGET_ARCH_IS_X86_64)
+#if !defined(LIBC_TARGET_ARCH_IS_X86)
 #error "Invalid file include"
 #endif
 
 namespace LIBC_NAMESPACE_DECL {
 
+#ifdef __i386__
+[[gnu::naked]]
+LLVM_LIBC_FUNCTION(void, longjmp, (jmp_buf, int)) {
+  asm(R"(
+      mov 0x4(%%esp), %%ecx
+      mov 0x8(%%esp), %%eax
+      cmpl $0x1, %%eax
+      adcl $0x0, %%eax
+
+      mov %c[ebx](%%ecx), %%ebx
+      mov %c[esi](%%ecx), %%esi
+      mov %c[edi](%%ecx), %%edi
+      mov %c[ebp](%%ecx), %%ebp
+      mov %c[esp](%%ecx), %%esp
+
+      jmp *%c[eip](%%ecx)
+      )" ::[ebx] "i"(offsetof(__jmp_buf, ebx)),
+      [esi] "i"(offsetof(__jmp_buf, esi)), [edi] "i"(offsetof(__jmp_buf, edi)),
+      [ebp] "i"(offsetof(__jmp_buf, ebp)), [esp] "i"(offsetof(__jmp_buf, esp)),
+      [eip] "i"(offsetof(__jmp_buf, eip)));
+}
+#else
 [[gnu::naked]]
 LLVM_LIBC_FUNCTION(void, longjmp, (jmp_buf, int)) {
   asm(R"(
@@ -38,5 +60,6 @@ LLVM_LIBC_FUNCTION(void, longjmp, (jmp_buf, int)) {
       [r15] "i"(offsetof(__jmp_buf, r15)), [rsp] "i"(offsetof(__jmp_buf, rsp)),
       [rip] "i"(offsetof(__jmp_buf, rip)));
 }
+#endif
 
 } // namespace LIBC_NAMESPACE_DECL

libc/src/setjmp/x86_64/setjmp.cpp

@@ -11,12 +11,37 @@
 #include "src/__support/macros/config.h"
 #include "src/setjmp/setjmp_impl.h"
 
-#if !defined(LIBC_TARGET_ARCH_IS_X86_64)
+#if !defined(LIBC_TARGET_ARCH_IS_X86)
 #error "Invalid file include"
 #endif
 
 namespace LIBC_NAMESPACE_DECL {
 
+#ifdef __i386__
+[[gnu::naked]]
+LLVM_LIBC_FUNCTION(int, setjmp, (jmp_buf buf)) {
+  asm(R"(
+      mov 4(%%esp), %%eax
+
+      mov %%ebx, %c[ebx](%%eax)
+      mov %%esi, %c[esi](%%eax)
+      mov %%edi, %c[edi](%%eax)
+      mov %%ebp, %c[ebp](%%eax)
+
+      lea 4(%%esp), %%ecx
+      mov %%ecx, %c[esp](%%eax)
+
+      mov (%%esp), %%ecx
+      mov %%ecx, %c[eip](%%eax)
+
+      xorl %%eax, %%eax
+      retl)" ::[ebx] "i"(offsetof(__jmp_buf, ebx)),
+      [esi] "i"(offsetof(__jmp_buf, esi)), [edi] "i"(offsetof(__jmp_buf, edi)),
+      [ebp] "i"(offsetof(__jmp_buf, ebp)), [esp] "i"(offsetof(__jmp_buf, esp)),
+      [eip] "i"(offsetof(__jmp_buf, eip))
+      : "eax", "ecx");
+}
+#else
 [[gnu::naked]]
 LLVM_LIBC_FUNCTION(int, setjmp, (jmp_buf buf)) {
   asm(R"(
@@ -41,5 +66,6 @@ LLVM_LIBC_FUNCTION(int, setjmp, (jmp_buf buf)) {
       [rip] "i"(offsetof(__jmp_buf, rip))
       : "rax");
 }
+#endif
 
 } // namespace LIBC_NAMESPACE_DECL