fix: reg allocator crashes on SAL / SAR instructions

Mati365 · Jan 21, 2024 · b358fcf · b358fcf
1 parent 97c4dac
commit b358fcf
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Showing 3 changed files with 50 additions and 10 deletions.
diff --git a/...ages/compiler-pico-c/src/arch/x86/backend/compilers/math/int/compileIntMathInstruction.ts b/...ages/compiler-pico-c/src/arch/x86/backend/compilers/math/int/compileIntMathInstruction.ts
@@ -48,6 +48,13 @@ export function compileIntMathInstruction({
   switch (operator) {
     case TokenType.BIT_SHIFT_RIGHT:
     case TokenType.BIT_SHIFT_LEFT: {
+      const rightAllocResult = regs.tryResolveIrArg({
+        size: biggestArgSize,
+        arg: rightVar,
+        allowedRegs: ['cl', 'cx'],
+        allow: IRArgDynamicResolverType.REG | IRArgDynamicResolverType.NUMBER,
+      });
+
       const leftAllocResult = regs.tryResolveIRArgAsReg({
         size: biggestArgSize,
         arg: leftVar,
@@ -59,15 +66,8 @@ export function compileIntMathInstruction({
         });
       }
 
-      const rightAllocResult = regs.tryResolveIrArg({
-        size: biggestArgSize,
-        arg: rightVar,
-        allowedRegs: ['cl', 'cx'],
-        allow: IRArgDynamicResolverType.REG | IRArgDynamicResolverType.NUMBER,
-      });
-
       const opcode = operator === TokenType.BIT_SHIFT_RIGHT ? 'sar' : 'sal';
-      const asm: string[] = [...leftAllocResult.asm, ...rightAllocResult.asm];
+      const asm: string[] = [...rightAllocResult.asm, ...leftAllocResult.asm];
 
       if (rightAllocResult.value === 'cx') {
         asm.push(

diff --git a/packages/compiler-pico-c/src/arch/x86/backend/reg-allocator/int/X86BasicRegAllocator.ts b/packages/compiler-pico-c/src/arch/x86/backend/reg-allocator/int/X86BasicRegAllocator.ts
@@ -512,7 +512,10 @@ export class X86BasicRegAllocator {
 
     if (!result) {
       if (query.size) {
-        const [reg] = query.allowedRegs ?? ['ax'];
+        const [reg] = query.allowedRegs?.filter(
+          allowedReg => getX86RegByteSize(allowedReg) === query.size,
+        ) ?? ['ax'];
+
         const spillVar = stackFrame.allocSpillVariable(query.size);
         const ownerships = ownership.getOwnershipByReg(reg);
 

diff --git a/packages/compiler-pico-c/tests/codegen/statements/math.test.ts b/packages/compiler-pico-c/tests/codegen/statements/math.test.ts
@@ -19,8 +19,8 @@ describe('Math', () => {
       sub sp, 4
       mov word [bp - 2], 14     ; *(a{0}: int*2B) = store %14: int2B
       mov word [bp - 4], 4      ; *(c{0}: int*2B) = store %4: int2B
-      mov ax, [bp - 2]
       mov cx, [bp - 4]
+      mov ax, [bp - 2]
       sal ax, cl                ; %t{2}: int2B = %t{1}: int2B bit_shift_left %t{0}: int2B
       sar ax, 2                 ; %t{4}: int2B = %t{2}: int2B bit_shift_right %2: char1B
       mov word [bp - 2], ax     ; *(a{0}: int*2B) = store %t{4}: int2B
@@ -30,6 +30,43 @@ describe('Math', () => {
     `);
   });
 
+  test('bit shift with exhausted regs', () => {
+    expect(/* cpp */ `
+      int main() {
+        const char *ptr = "Hello world!";
+        int bs = sizeof(int)*8;
+        int mi;
+        mi = (1 << (bs-1)) + 1;
+        asm("xchg bx, bx");
+        return 0;
+      }
+    `).toCompiledAsmBeEqual(`
+      cpu 386
+      ; def main(): [ret: int2B]
+      @@_fn_main:
+      push bp
+      mov bp, sp
+      sub sp, 6
+      mov bx, @@_c_0_           ; %t{0}: const char*2B = lea c{0}: const char[13]*2B
+      mov word [bp - 2], bx     ; *(ptr{0}: const char**2B) = store %t{0}: const char*2B
+      mov word [bp - 4], 16     ; *(bs{0}: int*2B) = store %16: int2B
+      mov ax, [bp - 4]
+      sub ax, 1                 ; %t{2}: int2B = %t{1}: int2B minus %1: char1B
+      mov cx, ax
+      mov ax, word 1
+      sal ax, cl                ; %t{3}: int2B = %1: char1B bit_shift_left %t{2}: int2B
+      add ax, 1                 ; %t{4}: int2B = %t{3}: int2B plus %1: char1B
+      mov word [bp - 6], ax     ; *(mi{0}: int*2B) = store %t{4}: int2B
+      xchg bx, bx
+      mov ax, word 0
+      mov sp, bp
+      pop bp
+      ret
+      @@_c_0_:
+      db "Hello world!", 0x0
+    `);
+  });
+
   test('int b = 1 + ~a', () => {
     expect(/* cpp */ `
       void main() {